Best utility knives for plumbers

The Klein Tools 44130 is a folding lockback utility knife: a utility knife and a razor knife in one, with a push-button open and close. Open, it's 7.125 inches long. Closed, it's 4.125 inches, small enough for a pouch pocket or a back pocket.

The blade change is why it's my pick. Klein calls it auto-loading, a three-step change that it says keeps your exposure to the blades to a minimum. You push the blade release button to remove the old blade, slide the lever back, and push it out again to release the new one. An internal storage area holds up to three blades.

That matters on a plumbing job because you change blades often. Drywall paper and cardboard dull an edge fast, and a dull blade tears drywall instead of scoring it. A blade change you can do quickly in a crawlspace or under a sink means you're more likely to actually do it.

The blades are triple ground, which Klein says keeps them sharp longer, and they have a wire-stripping notch. That notch is useful when you're wiring a disposal, a water heater thermostat or a recirculation pump. Turn the power off at the breaker first. Klein's own warning is never to use the knife on or near live circuits.

The 44130 takes standard utility blades and comes with three. Klein lists the blade as 440A stainless steel. You don't need Klein's own blades to keep it going, so a box of standard blades from the supply house fits.

The handle is aluminum with rubber grips, which Klein says improve control and comfort. The handle is bright orange, so it's easier to find in a dark tool bag or on a crawlspace floor.

At 7.5 ounces (213 grams), it's the heaviest Klein on this page. It doesn't have the 44303's strap-cutting slot or the 44306's scraper. If those matter more than the auto-loading change and the wire notch, look at those two below.

The Stanley Classic 99 is the retractable utility knife Stanley has made since 1952. It's 6 inches long with a precision die-cast zinc body that Stanley calls strong and lightweight. It doesn't fold. The blade slides out of the nose and back in.

Blade storage is the reason it's here. Stanley says the handle holds up to 10 blades. On a day of cutting drywall access holes, where blades dull quickly, you can carry a fresh supply inside the knife instead of a separate dispenser.

The InterLock nose is Stanley's name for the front of the body, and Stanley says it firmly secures the blade for safe, accurate cuts. A blade that doesn't wobble in the nose makes a straighter score line on drywall paper.

It ships with three Stanley 11-921 utility blades, and the blade is carbon alloy steel, according to Stanley. It takes standard utility blades, so the same box you buy for other knives fits this one. That's handy when one box of blades has to serve several knives on the truck.

One thing Stanley's page doesn't agree with itself on is the number of blade positions. The overview says 3 positions, and the feature list says 5. Either way, you can set how far the blade sticks out. A shorter blade is useful for scoring drywall paper without cutting into a pipe or wire behind it.

The trade-off is shape. A fixed retractable knife is bulkier than a folder, and Stanley doesn't list a pocket clip. It rides in the tool bag or a pouch, not a jeans pocket. Stanley also doesn't list a weight on the page I read.

If you already carry a folder, this is a good second knife to leave in the drywall bag with its own blade supply.

The Klein 44303 is a compact folding utility knife from Klein's FlickBlade line. It's 6.9 inches open, 4.5 inches closed and 4.6 ounces, with an aluminum handle and a belt clip. It's the lightest knife on this page with a listed weight.

The strap slot is what earns its label. Klein puts a slot on the top back of the handle that cuts straps with the knife closed. Water heaters, tub surrounds and boxes of fittings come strapped, and cutting those without opening the blade keeps a sharp edge away from your hand and the carton.

The blade locks open at two angles: 135 degrees or 180 degrees. The straight 180 is for everyday cutting. The angled 135 position puts your hand above the surface, which helps when you slice a caulk line along a tub deck or score along the floor.

Opening is a side button release. Klein calls it intuitive and quick. Closed, the blade sits inside the aluminum handle. The belt clip holds it on a pocket edge or a belt, so it's within reach when a delivery shows up.

Blade storage is built in. A fold-out holder stores five extra blades, and Klein includes them, so the knife comes with six in total. That's enough for a few days of drywall cuts before you need a new box.

There's a tether hole at the back of the handle. If you work from a ladder in a stairwell or above a drop ceiling, a tether keeps the knife from falling onto someone below.

What it doesn't list is a wire-stripping notch, which the 44130's blades have, or a scraper, which the 44306 has. For a knife that lives in your pocket for boxes, straps and drywall, it's the one I'd carry.

The Klein 44306 is a FlickBlade folding knife that switches between a utility knife and a scraper. Klein writes it up for cutting and scraping tasks, and the scraper is the reason a plumber would pick it over the 44303.

Caulk and putty jobs are where it fits. Pulling a toilet or replacing a tub spout leaves a ring of old caulk or putty behind. You slice the bead with the blade, then scrape the surface clean so new sealant has something to stick to. With the 44306, that's one tool instead of a knife and a separate scraper.

It has two locking positions, which Klein describes as angled for specialized tasks or standard for everyday cutting. The angle helps on flat work like a tub deck or a floor, where a straight blade would put your knuckles on the surface.

The body is aluminum, and Klein says it resists drops and impacts. Open, it's 7.53 inches. Closed, it's 5.08 inches, the longest of the Kleins on this page. It weighs 5.9 ounces, or 167 grams.

Klein includes three carbon steel utility blades and says the knife takes universal utility blades. The listed blade is 2.42 inches long and 0.75 inch wide, the size of a standard utility blade, so supply-house blades fit.

Storage is the weak point next to the 44303. The 44306's built-in compartment holds one extra blade, not five. Klein doesn't list a strap slot or a wire-stripping notch for it either. Since it takes universal blades, a box of standard blades in the truck keeps it going.

If your week has more caulk lines than cardboard, this is the folder I'd clip on. If it's mostly deliveries and drywall, the 44303 or 44130 fits better.

The OLFA L-5 is an 18mm snap-off utility knife. OLFA invented the snap-off knife, and it writes the L-5 for construction, flooring, drywall and general jobsite cutting. Its applications list includes gaskets, plastic straps, flexible plastics, plastic sheeting and house wrap.

Gaskets are why it's on a plumber's list. When the right gasket isn't on the truck, you cut one from sheet stock. A long blade that you can extend and lock lets you follow a curve around a flange in one pass. The L-5's ratchet lock, which OLFA says uses a wheel, holds the blade at any length you set.

The snap-off blade gives you a fresh tip without changing the blade. The preloaded LBB blade has eight segments, and OLFA says it's 25 percent sharper than standard blades. When the tip dulls, you snap off one segment and keep cutting.

The handle is fiberglass-reinforced with a wraparound anti-slip rubber grip, and OLFA says it's chemical resistant for easy cleanup. That's handy after cutting through old caulk, adhesive or pipe dope. A stainless steel channel holds the blade in place, and the blade change needs no tools.

There's also a metal pick built in. OLFA says it's for tasks where you shouldn't use your blade tip, like opening paint cans, removing plate covers and cleaning out caulk. On a plumbing job, that's the lid on a can of primer or old caulk in a corner.

The L-5 takes most OLFA 18mm blades, including hook and serrated versions. It doesn't take standard trapezoid utility blades, so it needs its own blade supply.

The listing linked here is the genuine OLFA L-5, sold by a third-party seller and in stock on the day of the update. OLFA doesn't publish a weight on its product page.