• SkillCat Team

All about Wrenches

Updated: Jul 6

Key Hand Tools: Chapter 4


Intro to Wrenches


In this module, you will learn:

- What a wrench is,

- How to use a wrench, and

- What wrench holdback is Skip to quiz!


How to Use A Wrench


A wrench is a common hand tool used to tighten or loosen nuts and bolts. Every wrench has two parts:

  • The head, and

  • The handle


The head of the wrench is used to grip nuts or bolts. The handle of the wrench is where you will hold the wrench when tightening or loosening fasteners.


All wrenches will tightly grip the head of a fastener. Once the head of the wrench grips the fastener, you can rotate the wrench to tighten or loosen the nut.


Wrenches have long handles. The long handle gives you more leverage than other tools. More leverage makes it easier to tighten or loosen a fastener.


You will use your dominant hand to hold the wrench. The handle of the wrench will run across your palm and in between your thumb and pointer finger. Your fingers should close around the handle.


Recall that a longer handle gives you more leverage. Hold the wrench near the end of the handle for the greatest amount of leverage.


When choosing a wrench, you will choose one that is slightly larger than the diameter of the bolt head. Recall that we measure bolts in inches. For example, you may see a bolt measured in 4/16” or 1/4".


Wrenches have two types of sizing:

  • Imperial, and

  • Metric

In an imperial wrench, the measurement is in fraction of inches like 1/4" and 9/16”. In a metric wrench, the measurement is in whole millimeter figures like 10mm or 8mm.


When you mount the head of the wrench to a fastener, the nut or bolt head should be deep into the jaws of the wrench. In the picture to the right, you can see proper vs improper contact. Always make sure the jaws are secured to the nut head.


If a wrench is not the correct size or it is not properly placed on the fastener, the wrench can slip off the nut or bolt. When the wrench slips off the nut or bolt, it is called wrench slippage. Wrench slippage can injury you. You will be applying large amounts of force to the handle when it slips.


To avoid wrench slippage, make sure your wrench is the correct size and in proper contact with the bolt or nut. It is also important to not pull the wrench at an angle to the fastener. You should be pulling the wrench at a 90-degree angle to the fastener.


It is important to pull the wrench towards you when tightening or loosening a nut or bolt. Pulling the wrench towards you reduces the risk of injury. If the wrench slips, you are not at risk of slamming your hand into an object.


When you try to loosen a nut or a bolt, the nut and bolt may spin at the same time. If this happens, the nut will not loosen even as you rotate the wrench. To prevent the nut and bolt from spinning at the same time, we use a technique called a holdback.


A holdback is when you grip the nut with a wrench, and the bolt with another wrench. One wrench prevents the bolt from rotating. The other wrench is used to loosen the nut. Holdback helps prevent the nut and bolt from moving in the same direction.


In this module you learned:

  • What a wrench is,

  • How to use a wrench, and

  • What wrench holdback is

Wrenches are excellent at tightening or loosening large nuts and bolts.




Types of Wrenches - Part 1


In this module, you will learn:

- How to use an open wrench, and

- How to use a box wrench Skip to quiz!


Types of Wrenches


In this module, you will learn about two common wrenches:

  • Open wrenches, and

  • Box wrenches


Open Wrench


An Open Wrench has a U-shaped head on both sides of the handle. The two heads are different sizes. The two sizes let you work on multiple sized nuts or bolts with one wrench.


An open wrench is great for reaching nuts or bolts in hard to reach spaces. Open end wrenches have a higher chance of slipping off the nut or bolt.

To use an open wrench, start by identifying the correct size open end wrench for the nut or bolt. Insert the nut or bolt head into the jaws of the open end wrench. Make sure that the jaws of the wrench are in solid contact with the head of the bolt. The bolt should be deep into the U of the wrench jaws.


To tighten a nut or bolt with an open wrench, turn the wrench clockwise. To loosen a nut or bolt with an open wrench, turn the wrench counterclockwise. Remember “Righty tighty, lefty loosey.”


In some cases, you will not be able to rotate the wrench in a full circle. If this happens, you must reset the wrench jaws after each turn.


Rotate the wrench as much as you can. Remove the jaws from the fasteners. Place the jaws back on the fastener. Rotate the wrench again. Repeat this process until the fastener is tight or loose.


Box Wrench


A box wrench looks similar to an open wrench, but it has ring-shaped heads on both sides of the handle. The two heads are different sizes. The two heads let you work on multiple sized nuts or bolts with one wrench.


Box wrenches provide more contact with the bolt head than an open wrench. More contact between the box wrench and the bolt head increases the wrench’s grip on the fastener. Additional grip reduces the chance of a wrench slipping off the bolt head.


To use a box wrench, start by identifying the correct size box end wrench for the nut or bolt. Insert the nut or bolt head into the jaws of the box wrench. Make sure that the nut is firmly secure in the box head.


To tighten a nut or bolt, turn the wrench clockwise. To loosen a nut or bolt, turn the wrench counterclockwise. Remember “Righty tighty, lefty loosey.”


In this module you learned about two types of wrenches including:

  • Open wrenches, and

  • Box wrenches,

The open wrench is great for hard to reach nuts or bolts. The box wrench gives you more grip on the fastener. It is great for very tight nuts or bolts



Types of Wrenches - Part 2


In this module, you will learn about:

- More types of wrenches, and

- Wrench safety Skip to quiz!


Types of Wrenches


In addition to open and box wrenches, there are:

  • Combination wrenches,

  • Crescent wrenches, and

  • Socket wrenches.


Combination Wrench


A combination wrench has one head that is U-shaped and another head that is ring shaped. A combination wrench combines the open wrench and box wrench into one. The heads on a combination wrench will be the same size.


The combination wrench gives you the benefits of the box and open wrenches. You can use the box end to loosen a very tight bolt. You can use the open end to reach nuts in hard to reach areas.



Crescent (Adjustable) Wrench


A Crescent Wrench, also called an adjustable wrench, has an adjustable jaw size. The adjustable jaw allows you to use the wrench on different sizes of nuts and bolts. With a crescent wrench, you do not need to find a specific wrench for a bolt or nut. You can adjust the jaw to the fastener.


A crescent wrench has a “warm screw” just above the handle. Turn the warm screw to increase or decrease the width of the jaws. You can see the warm screw highlighted in the image to the right.


To use a crescent wrench, start by making sure that your crescent wrench jaws can fit the nut or bolt you are working on. Twist the screw until the jaws are slightly larger than the nut. Place the nut inside the jaws of the crescent wrench.


Once the nut is inside the jaws, turn the warm screw to slowly tighten the jaws of the adjustable wrench. Once the jaw is tight around the nut, you can begin to tighten or loosen the nut. Rotate the wrench clockwise to tighten the nut. Rotate the wrench counterclockwise to loosen the nut.


When you rotate the wrench, it is important that the force is directed into the fixed jaw. To do this, the fixed jaw should always be on the opposite side of the turning direction. See the graphic for an example of how to rotate the wrench.


Socket Wrench


A socket wrench has a handle, a head with a square extension coming out of the head, and a socket. You can see an example of a socket wrench in the image to the right.


Sockets allow you grip different sized nuts or bolts. The socket locks onto the square extension on the wrench head. The head of different sized nuts or bolts can be inserted into the socket.


The socket functions similarly to a box end wrench. The nut or bolt head will fit into the hollow opening of the socket. Unlike the box wrench, you can change sockets for different sized nuts. This makes socket wrenches useful in any situation.


With an open wrench, you have to adjust the jaw position with each turn. A socket wrench has a ratchet which makes it easier to quickly tighten or loosen nuts compared to other wrenches.


With a socket wrench, you do not need to reset the wrenches head position with each pull. As you rotate the wrench back to the starting position, the ratchet does not turn the nut or bolt. The ratchet only turns the nut or bolt when you are rotating the wrench in a specific direction.


A socket wrench can loosen or tighten based on its knob setting. To change the direction in which the socket turns, flip the knob on the head of the wrench.


For example, if the knob is switched to one setting the socket wrench will only grip the nut when you rotate the wrench clockwise. If the knob is switched to the other setting, the wrench will only grip the nut when you rotate the wrench counterclockwise.


Recall, that a socket wrench can have different sized sockets attached to it. To change a socket, press the quick release button on the back of the socket wrench. Pull the socket away from the head of the wrench and the socket will come off.


To add a new socket, press the quick release button of the back of the head of the wrench. Slide the socket onto the square extension of the wrench. Release the quick release button when the socket is fully on the wrench. Pull the socket to confirm it is secure.


To use a socket wrench, start by attaching the correct size socket for the nut or bolt you are working on. Set the direction of the knob on the socket wrench to tighten or loosen. Press the socket onto the head of the nut so there is full contact.


Rotate the socket wrench clockwise to tighten the nut. Rotate the socket wrench counterclockwise to loosen the nut. When you cannot rotate the wrench further, move the handle back to the starting position. Rotate the wrench again.


Before using a wrench, inspect the wrench for damage. Do not use a bent, cracked or damaged wrench. Using a damaged wrench can result in injury.


Do not use a wrench on moving machinery. It can be very dangerous. Do not use a wrench to strike objects. If you need to strike an object, use a hammer. Do not strike a wrench with a hammer to gain more force.


In this module you learned about several types of wrenches including:

  • A combination wrench,

  • A crescent wrench, and

  • A socket wrench


The combination wrench combines the open and box wrenches. The crescent wrench has an adjustable jaw. The socket wrench has a ratcheting mechanism that makes it easier to tighten or loosen fasteners.




Specialized Wrenches - Part 1


In this module, you will learn about:

- Additional types of wrenches,

- How to use each wrench, and

- When to use each wrench Skip to quiz!


Types of Wrenches


In addition to what we covered in common wrenches, there are wrenches designed for specific situations.


Some common specialized wrenches are:

  • Allen wrenches, and

  • Pipe Wrenches


Allen Wrench


The first wrench we will cover is an allen wrench. An allen wrench has an L-shaped body with a hexagonal head at each end. An allen wrench is used when tightening and loosening bolts with hexagon shaped sockets on their heads.

Recall, a longer wrench gives you more leverage. An allen wrench has a hexagonal head at both ends of the wrench. You can insert either end of the allen wrench into a hexagonal head, but each end has unique advantages.


If you insert the allen wrench so that the wrench is vertical, you will have less leverage. Since this position has less leverage, you will need to work harder to rotate the wrench. This position can make it easier to reach hard to reach areas.


You gain leverage by inserting the allen wrench at a 90 degree angle to the nut. The additional leverage in this position makes it easier to loosen very tight bolts. In general, the long lever position is the best one to use.


Pipe Wrench


A pipe wrench is designed to be used on soft piping, like black pipe. The pipe wrench has an adjustable jaw that lets you work on a variety of pipe sizes. The jaws of a pipe wrench also have sharp teeth which give it a better grip on pipes.


The pipe wrench has four parts:

  • The handle,

  • The adjustable nut,

  • The fixed jaw, and

  • The adjustable jaw

You can see each section in the image to the right.


You hold the pipe wrench at the end of the handle for maximum leverage. The adjustable nut is a rotating dial that you twist to increase or decrease the size of the jaws.


All pipe wrenches have a fixed jaw and an adjustable jaw. The fixed jaw does not move. It is “fixed” into one position. The adjustable jaw will move up and down as you rotate the adjustable nut.


The adjustable jaw also has a rocker built into the jaw. The rocker allows the fixed jaw to hook onto pipe. It also allows you to easily reposition the jaw.


A pipe wrench has an adjustment nut that moves the jaws closer or farther apart. Move the adjustable nut clockwise to bring the jaws closer together. Move the adjustable nut counterclockwise to move the jaws farther apart.


A pipe wrench is used for tightening or loosening piping. The sharp teeth on a pipe wrench give you extra grip as you rotate the wrench. Pipe wrenches are longer than other wrench types. The longer wrench provides more leverage.


To use a pipe wrench, start by rotating the adjustment nut until the pipe jaws are slightly larger than the pipe. Place the pipe in between the jaws. The pipe should not be touching the back of the jaw. You can see an example of proper contact in the image to the right.


Rotate the adjustment nut until the pipe jaws are lightly biting into the soft pipe. When using a pipe wrench, you want the force to go into the fixed jaw. To do this, the opening in the jaws should be facing in the direction you will rotate the wrench.


For example, in the image to the right you want to rotate the handle clockwise. If you rotate the handle clockwise, you will be moving in the direction of the open jaws. If you try to rotate the pipe wrench in the wrong direction, the rocker will unhook the wrench.


Like with other wrenches, always position yourself so that you pull the wrench towards you. Pulling the handle towards you is safer and prevents smashing your knuckles into objects. Rotating the wrench clockwise will tighten the pipe. Counter clockwise will loosen the pipe.


Once you have rotated the pipe, you can bring the pipe back to the starting position. Similar to the socket wrench, the adjustable jaw on the pipe wrench only pulls in one direction. This allows you to easily make multiple turns of the wrench without having to remove the wrench from the piping.


Once the pipe is loosened, we need to remove the pipe wrench from the pipe. Press down on the adjustment nut and the adjustable jaw will loosen from the pipe. Pull the pipe wrench away from the pipe.


When you are using a pipe wrench, you must be careful what material you place the wrench on. The teeth of the pipe wrench can damage softer materials like brass. The teeth can also damage pipe threading, nuts, bolts, and other fasteners.


Using two pipe wrenches might be necessary when connecting two free moving pieces of pipe. One wrench is used to hold one piece of piping in place. The other wrench is used to tighten or loosen the other pipe.


In the image to the right, you can see two pipe wrenches. One wrench is on a T union. The other wrench is on black piping. The wrench on the T union prevents the union from moving. The wrench on the piping will be rotated to loosen the pipe.


To tighten the two pipes together, move the pipe wrench that is closest to you clockwise and the other wrench counterclockwise. To loosen the two pipes, move the pipe wrench that is closest to you counterclockwise and the other wrench clockwise.


When choosing a pipe wrench, pick one that is suitable for the pipe you are working with. A pipe wrench that is too large is harder to turn and can damage smaller pipe. A pipe wrench that is too small will not have the grip to turn larger pipes.


There are multiple types of wrenches specifically made for certain types of jobs. In this module, you learned about:

  • Allen wrenches, and

  • Pipe Wrenches


Allen wrenches have two positions. The short lever position gives you more leverage. The pipe wrench is used to tighten or loosen piping. Do not use the pipe wrench on brass fittings, bolts, nuts, or threading.




Specialized Wrenches - Part 2


In this module, you will learn about:

- Additional types of wrenches,

- How to use each wrench, and

- When to use each wrench

This module is part 2 of specialized wrenches. Finish part 1 before beginning this module. Skip to quiz!


Types of Wrenches


In addition to what we covered in common wrenches, there are wrenches designed for specific situations.


Some common specialized wrenches are:

  • Breaker bars,

  • Torque wrenches, and

  • Service wrenches


Breaker Bar


Recall, a longer handle on a wrench creates more leverage. A breaker bar is a long bar that attaches to a socket wrench to give you more leverage.


A breaker bar is used in the same way as a socket wrench. Turn the breaker bar clockwise to tighten and counterclockwise to loosen. A breaker bar should be used when nuts are difficult to remove.



Torque Wrench


Recall that each type of bolt and nut have specific torque requirements. Applying too much torque can damage the fastener. Applying too little torque weakens the fastener.


A torque wrench allows you to adjust the torque you are applying to a bolt. This helps to prevent under or over tightening a fastener. A torque wrench looks functions in a similar way to a socket wrench.


The torque wrench has several parts including:

  • The head,

  • The socket,

  • The rotating handle,

  • The measurement marks, and

  • The nut


The nut on the bottom of the handle prevents the handle from moving. If the nut is loose, you can rotate the handle. Rotating the handle to the right will move the handle up the shaft of the torque wrench.

As the handle moves up the torque wrench, the wrench is set to a higher level of torque. You can see what torque the wrench is set to by looking at the top of the handle and the gauge marks.


To use a torque wrench, start by setting the wrench to the required torque. Loosen the nut at the bottom of the handle. Rotate the handle of the wrench until the handle is lined up with the correct measurement mark.


Set the socket size of the torque wrench to the size of the nut you are working on. Press the torque wrench onto the nut. Turn the wrench clockwise to tighten the nut. Turn the wrench counterclockwise to loosen the nut.


Continue rotating the wrench until the nut is loose or tight. Once you finish, set the torque wrench to its lowest measurement.


A torque wrench is best used when you don’t want to over tighten a bolt. They are commonly used when working on engines. An over tightened bolt can cause an engine to crack.


A torque wrench can measure force in multiple units such as:

  • lb-ft (pound-foot)

  • lb-in (pound-inch)

  • Nm (Newton-meter)

You will see all units on the handle measurements.


Service Wrench


Service wrenches, or pump wrenches, are lighter wrenches that are used in low force jobs. They are easy to carry and provide delicate force for certain jobs.


Service wrenches are commonly used in the HVAC industry

They are great for

-Opening and closing gas tanks,

-Adjusting thermostat valves,

-Opening and Closing valves


In this module, you learned about:

  • Breaker bars,

  • Torque wrenches, and

  • Service wrenches


A breaker bar attaches to a socket wrench to give you more leverage. A torque wrench allows you to set the torque to a specific amount. A service wrench is used for delicate job like adjusting valves.



Question #1: What should you do to avoid wrench slippage?

  1. Ensure proper contact with the wrench and bolt head.

  2. Pull on the wrench instead of pushing it.

  3. Pull on the wrench at a straight angle with the head of the bolt.

  4. All of the above.

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Answer: All of the above.

Proper head contact, pulling on the wrench, and not pulling at odd angles helps prevent wrench slippage.


Question #2: Why is wrench holdback useful?

  1. It prevents the nut and bolt from spinning in the same direction.

  2. It allows you to use any sized wrench.

  3. It moves the nut and bolt in the same direction.

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Answer: It prevents the nut and bolt from spinning in the same direction.

Wrench holdback turns the nut and bolt in opposite directions at the same time. This makes the tightening and loosening of a nut and bolt faster.


Question #3: The open end wrench has:

  1. A higher chance of slipping

  2. A closed jaw

  3. A very short handle

  4. Only one head

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Answer: A higher chance of slipping

The open end wrench has a higher chance of slipping off a fastener. The open jaws cause the wrench to slip if the wrench is not at a 90 degree angle with the fastener.


Question #4: The box wrench has:

  1. More contact with the fastener than an open wrench

  2. Two heads

  3. Less chance of slipping

  4. All of the above

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Answer: All of the above

The box wrench has more contact with the fastener since it forms a circle around the fastener. It also has two heads and less chance of slipping.


Question #5: Which wrench is best for providing turning force and loosening hard to reach nuts?

  1. Open wrench

  2. Box wrench

  3. Crescent Wrench

  4. Combination Wrench

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Answer: Combination Wrench

A box wrench has multiply points of contact to provide more turning force. An open wrench has an open end to work on hard to reach fasteners or quickly loosen one. A combination wrench has a box end to loosen tight bolts and an open end to then quickly remove those bolts.


Question #6: When might you use a socket wrench?

  1. When tightening and loosening pipe.

  2. When removing different sized nuts and bolts.

  3. When loosening a really tight bolt.

  4. When you can’t find the correct sized wrench.

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Answer: When removing different sized nuts and bolts.

A socket wrench has different sized sockets that you can attach to fit different sized nuts and bolts.


Question #7: Why is a crescent wrench useful?

  1. It provides more turning force.

  2. It does not need to be constantly adjusted.

  3. It has an adjustable jaw to fit different sized bolts.

  4. It it lightweight.

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Answer: It has an adjustable jaw to fit different sized bolts.

A crescent wrench has an adjustable jaw that can open and close to fit different sized bolts.


Question #8: When would it be best to use a box wrench?

  1. To quickly remove a bolt.

  2. When loosening different sized bolts.

  3. When wanting to easily attach to a bolt head.

  4. To loosen a tight bolt.

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Answer: To loosen a tight bolt.

A box wrench has multiple points of contact with a bolt and can provide extra turning force when loosening a bolt.


Question #9: Which is a proper form of wrench safety?

  1. Shimming wrenches of the incorrect size so they fit.

  2. Using a wrench on moving machinery

  3. Pulling on a wrench

  4. Using a bent wrench.

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Answer: Pulling on a wrench

Pushing on a wrench should be avoided as it can cause slippage and injury.


Question #10: A pipe wrench should not be attached to:

  1. Nuts

  2. Bolts

  3. Brass Fittings

  4. All of the above

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Answer: All of the above

The teeth of a pipe wrench are sharp and easily damage soft metal, nuts, and bolts.


Question #11: What should you do when attaching a pipe wrench to a pipe?

  1. Make sure the pipe wrench is pulling at an angle that is not straight.

  2. That the pipe wrench teeth are securely fixed to the pipe.

  3. That you are pulling near the top of the wrench.

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Answer: That the pipe wrench teeth are securely fixed to the pipe.

In order to use a pipe wrench correctly, the teeth of the pipe wrench must be securely attached to the pipe.


Question #12: What do breaker bars help provide?

  1. Leverage

  2. Turning Force

  3. A better angle to turn the wrench.

  4. All of the above.

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Answer: All of the above.

A breaker bar gives you a longer lever which allows you to turn the wrench with more force and at a better angle.


Question #13: When should you use a torque wrench?

  1. When removing multiple sizes of bolts.

  2. When working on steel beams.

  3. When you need a fastener tightened to a specific torque

  4. When loosening metal pipe.

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Answer: When you need a fastener tightened to a specific torque

Torque wrenches apply the right amount of force when screwing in bolts. You use a torque wrench to avoid over tightening which can cause cracking on a fragile material you are working on.


Question #14: Why should you lock the handle when tightening with a torque wrench?

  1. It prevents the torque setting from changing.

  2. It prevents slipping.

  3. It makes the wrench tighten instead of loosen.

  4. It gives the wrench more power.


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Answer: It prevents the torque setting from changing.

Locking the handle of a torque wrench locks in your torque setting. If not properly locked, your torque setting of the wrench could change while in use and over tighten your bolts.




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