How to Use a Wrench Like a Pro, According to a Renovations Expert

Beginner DIYers probably know that their toolkit should include a hammer and a screwdriver. But one tool that could get overlooked when you’re building your must-have home maintenance arsenal is at least one type of wrench. Yes, really! You might think this tool is for pros only, but knowing how to use a wrench (and having one handy) will save you some headaches. Trust me: I’ve been renovating and building for decades, so I know my stuff.

The basic job of a wrench is to tighten or loosen nuts and bolts — something you can’t do with any other tool. So if you have any nuts and bolts in your home (and who doesn’t?), a wrench is an essential tool for any repairs and projects. But a wrench can do its job only if it’s able to securely grip whatever it is you’re trying to turn, so the first rule of how to use a wrench is this: Choose a type of wrench that fits your fastener.

First things first: Not all wrenches are created equal. Fixed wrenches are designed to fit only specific sizes of nuts and bolts, while adjustable wrenches work with a variety of sizes. The fixed wrench designed for the specific nut or bolt you’re trying to turn will grip it best, but you’d need a lot of such wrenches to turn all the different nuts and bolts in your house.

You may prefer instead to have the “one wrench to turn them all” — an adjustable wrench — in your toolkit. But no matter what you choose, you’ll need to know how to wield it. Here’s a guide to how to use the most common types of wrenches.

Whether square or hexagonal, the heads of nuts and bolts have flat surfaces. The secret to using an open-ended wrench effectively is to choose one that fits tightly onto these flat surfaces. If the fit isn’t tight, the wrench will slip, and that can strip the head of the fastener — making the job of loosening or tightening it that much more difficult. 

If you know the size of the head in fractions of an inch or millimeters, it’s easy to choose the right wrench by simply noting the size marked on the handle. Otherwise, you have to eyeball it. When doing so, make sure the wrench is resting on the flat surfaces of the fastener head. If it is contacting the edges where the flat surfaces meet, it’s too big, and it will slip. 

Here’s how to use an open-ended wrench, step by step.

1. Slip the jaws onto the fastener from the side, not from the top. Once the wrench is seated, give the handle a little wiggle to make sure there’s no extra room.
2. Grip the handle as close to the end opposite the jaws as possible. The more distance there is between the jaws and your hand, the more force the tool will develop. 
3. Turn nuts and bolts clockwise to tighten them and counterclockwise to loosen them (righty-tighty, lefty-loosey). Note that to get the head to turn in one direction, you have to pull the handle in the opposite direction. 

Pro tip: If a fastener is stuck so firmly that the wrench begins to slip, stop immediately and lubricate the fastener with WD-40. If that doesn’t help, you need a box wrench.

The head of a box wrench forms a ring, and the insides of the ring are serrated to provide a better grip on a fastener head. The serrations, along with the closed head, help prevent the wrench from slipping off while you’re using it. Because of this, you can apply more torque than you can with an open-ended wrench of the same size.  

Pro tip: Box wrenches usually have heads on both ends of the handle, and they are slightly different sizes. If the head on one end doesn’t match your fastener, try the other one.

Here’s how to use a box wrench, step by step.

1. Set the head in place above the fastener, push down on the handle, and if the head slips all the way down without being forced, it’s probably the right size. 
2. Wiggle the handle to make sure the head fits tightly and there’s no play.
3. Torque the handle to the right to turn the head counterclockwise and loosen the fastener. Torque in the opposite direction to tighten the fastener. 

Pro tip: In tight spaces, you can sometimes move the handle only a short distance before encountering an obstruction. In this situation, there’s no alternative to lifting the head off the fastener and repositioning the wrench. This gets tiring when you have to do it repeatedly, so if you prefer something easier, consider getting a ratcheting box wrench.

You need a whole collection of box or open-ended wrenches if you want to be ready for every nut and bolt you are likely to encounter. The alternative is to have one or two adjustable wrenches (also called spanners) on hand for emergencies and special circumstances. 

A spanner has one fixed jaw and one movable jaw whose position you can adjust with a thumbscrew. This allows it to grip any size fastener that fits inside its jaws when they are fully extended. The drawbacks of this tool are that it’s bulkier than a fixed-head wrench and the jaws don’t grip as tightly. 

Here’s how to use an adjustable wrench, step by step.

1. Turn the thumbscrew to adjust the jaw opening to roughly the size of the fastener head, but a little larger. 
2. Slip the jaws onto the fastener from the side. 
3. Tighten the jaws securely onto the flat sides of the fastener head, using the thumbscrew.  Keep tightening until you can’t wiggle the handle. 
4. Keep the wrench handle on the same plane as the fastener while you use the wrench. If you lift or lower the handle even slightly, the head can slip. 

An L-shaped Allen wrench is a peculiar type of wrench: Instead of gripping the sides of a fastener head, it fits inside a slot on the head, like a screwdriver would. Some people call it a hex wrench because it has a hexagonal profile to match the hexagonal slot in the fastener.

As with any wrench, the size of an Allen wrench must match the size of the slot in the fastener. There aren’t that many sizes, though, and since there’s no such thing as an adjustable Allen wrench, most people purchase sets that include the most common sizes.

Here’s how to use an Allen wrench, step by step.

1. Insert the short end of the “L” into the slot on the fastener. If you’ve got the right size, the wrench will fit exactly and won’t wiggle when you try to move the other end. If the wrench wiggles or turns without moving the fastener, choose the next larger-size wrench from your set. 
2. Use the long end of the “L” as a lever to turn the fastener.
3. If you have too tight of a space to use the long end of the “L” as a lever, you can use the short end — but know that this will take longer.

Pro tip: Manufacturers like to use Allen nuts as set screws for towel racks, faucet handles and other common household items. Because the screws are so small and often close to a wall or other obstruction, it makes more sense to insert the long end of the “L” into the nut and use the short end to turn it. This works because you don’t need much leverage on small nuts.