How to Use a Utility Knife

Gear-obsessed editors choose every product we review. We may earn commission if you buy from a link. Why Trust Us?

It may seem like a simple tool, but there are several best practices to become a master with it.

Everybody needs a utility knife. Their versatility makes them indispensable. You can use a utility knife for opening cardboard boxes or cutting them into small pieces for recycling. You can cut drywall, carpet, shingles, packaging, packing tape, and plastic strapping. These tools can sharpen a carpenter's pencil or scribe a cut line on wood and even metal, particularly when you want to cut through a layer of paint or light rust.

And because of that, everybody needs to learn how to use one safely. These knives are equipped with a short, double-ended disposable blade. When one end of the blade is dull, remove it, flip it so the sharp end is out, and you’re back to cutting in no time. When both ends are dull, swap the blade out for a new one.

Most of these knives rely on slide-out (retractable) blades. But some use blades that pivot open (think of a folding knife), and a very few employ fixed blades (primarily used by specific trades, such as carpet installers where the sliding mechanism could get damaged during the work).

Below, we lay out some basic uses and share some safety tips. But first, some of our favorite types of utility knives and blades.

Utility knives come in a wide variety of configurations to suit you, your tool budget, and your preferences regarding durability, tool-free blade changing, handle shape, and even whether the tool has built-in extras (such as a twine cutter or a blade that converts to a scraper). Some utility knives even fold in half, like a pocket knife.

There are many folding utility knives today if you want both the benefit of a fixed blade (the blade does not slide into and out of the handle) and yet need the blade to be shielded when it's not in use. Some folding utility knives also incorporate the benefit of a folding design but have a retractable blade.

ToughBuilt has pioneered a new type of utility knife with a unique latching mechanism for its blade that allows you to toggle between using the tool as a utility knife and a razor scraper. The knife also features tool-free blade changing. Press the orange button at the knife's tip to release or insert a blade. The tool comes with a separate and easy-to-use blade magazine but has no onboard blade storage.

In direct contrast to such developments as that ToughBuilt is Stanley's 99E, now called the "Classic 99." It's a decades-old design that Stanley first sold in the early 1960s. The company modified the design such that the most recent models feature an interlocking nose feature. Both sides of the die-cast body interlock at the nose to prevent the halves from spreading apart under extreme force.

Utility knives have been the subject of intense engineering over the last 20 years, particularly in terms of how you change their blades. Tool-free blade swapping—along with tool-free access to the spare blade magazine—is a defining feature today. Although those are convenient features, the latches that allow them can be fouled by dirt, drywall dust, carpet fibers, and shingle particles. On the other hand, using a screwdriver to open a utility knife body can seem clumsy. Both types of blade changing (tool-free or those requiring a screwdriver) can be difficult to do on a cold winter day.

Stanley's 99E consists of two halves, one screw, and the spring steel blade carrier.

The "guts" of the Stanley are immediately apparent once you lift off its side. It's important to keep sawdust, drywall dust, and dirt out of the knife's cavity because contaminants can gum up the slide mechanism. On the other hand, it's easy to wipe clean. A drop of oil now and then on the blade carrier will keep it sliding smoothly.

The simple die-cast body has plentiful room in its handle for 10 blades.

Other knives use a simple push button or other latching mechanism to speed blade swapping. Keep the knife clean to avoid dirt buildup that can prevent these simple tool-free mechanisms from operating.

Some tool-free knives require a specialized blade; others take the standard blade with two U-shaped cutouts.

Most tool-free designs use some form of a button or thumb latch to secure the blade. The designs are such that it takes firm and deliberate pressure to unlock the blade; this prevents the blade from accidentally coming loose in handling or when you slide the knife into a tool bag.

Tool-free blade storage designs also rely on a simple latch that require firm pressure to engage.

In most cases, you’re holding what you cut with one hand and cutting with the utility knife in the other. That means if you don't watch where the holding hand is (and your wrist, and forearm), you can give yourself a nasty—even life-threatening—cut. I know a professional carpenter who did that and has an impressive scar on the inside of his forearm to show for it. And there are plenty more of these ghastly stories. I heard one just the other week about a carpenter that needed to be air-lifted to the emergency room because of such a cut.

To make sure you don't end up with one of these tales to tell:

Severing, scoring, and making thin carving cuts are jobs in which a utility knife excels. The emphasis here is on thin cutting. Note that a utility knife's blade is thin and not particularly long. When you bury it in a thick or tough cut, it won't do as well. That's why manufacturers make special hook-shaped blades for thick and tough materials, like roofing, carpet, and synthetic sheeting. Of course, the tool is essential for sharpening a carpenter pencil.

One of the most common uses of a utility knife is in drywall installation. Any utility knife works well for this, so long as you keep a reasonably sharp blade and keep the knife clean so that gypsum dust doesn't hang up the blade or prevents the blade magazine door from unlatching.

Although you don't need the knife to snap a sheet of drywall, you do need the knife again to cut the drywall's paper backing.

Professional carpenters and drywall installers often shorten a sheet or produce strips of drywall by guiding a utility knife with a tape measure.

The utility knife's point also scribes an extremely accurate cut line in wood and metal.

A utility knife can also score a line in metal. Although the tool works best on aluminum for this purpose, you can also use it on steel.

I’ve seen more than one contractor bag of debris with a utility knife blade poking right through the side. And I’ve also seen instances where the protruding blade has caught on walls, pricked people in the leg, or even caused the bag to rip open, spilling trash all over the floor. Solving that problem is a simple two-step process.

Roy Berendsohn has worked for more than 25 years at Popular Mechanics, where he has written on carpentry, masonry, painting, plumbing, electrical, woodworking, blacksmithing, welding, lawn care, chainsaw use, and outdoor power equipment. When he's not working on his own house, he volunteers with Sovereign Grace Church doing home repair for families in rural, suburban and urban locations throughout central and southern New Jersey.

Champion's RV-Ready Portable Generator Is 38% Off

The 10 Best Portable Air Purifiers of 2023

The Best Camp Stoves For Cooking Outdoors

The Best At-Home Solutions for Wildfire Smoke

The Best Camping Tents for Any Base Camp

This Hart Leaf Blower Bundle Is 64% Off at Walmart

The Best Binoculars for Getting a Closer Look

The 7 Best Kayaks for Fishing and Floating

Craftsman Mechanic Tool Set Is 35% Off at Lowe's

The 9 Best Slim Wallets to Suit Any Style

Transform Your Laptop Into a Portable Powerhouse

The Best Disposable Cameras for Making Memories