Best speed squares for plumbers

The Swanson S0101 is the square I'd put in a plumber's pouch first. It's the 7 inch Speed Square, CNC machined from heavy-gauge aluminum alloy to a 45° and 90° corner. Swanson invented the Speed Square in 1925, and the S0101 is still made in Frankfort, Illinois.

The corner is the reason it's my pick. Swanson cuts it on a CNC machine, and says the body is 15 times stronger than standard aluminum construction. A square that gets dropped off a ladder onto a slab needs to stay square, because every line you draw off it depends on that corner.

The markings are recessed into the aluminum and filled with black. Swanson's point is that surface etching can wear off under saw shoes, sweat and dust, while recessed marks stay readable. The finish is matte, so the scale doesn't throw glare back at you under a work light or outside.

The 7/8 inch heel is the lip that hooks the board edge. Hold it against a 2x4 and you get a square or 45° line in one motion, or a fence for a circular saw when you cut blocking. The 1/4 inch scribe bar holds a pencil tip at a fixed distance from that same edge for a parallel line.

Swanson calls it five tools in one: try square, miter square, saw guide, line scriber and protractor. The scales are degree, common rafter and hip/valley. Swanson's Blue Book, a pocket reference for roof pitch, rafter length and stair stringers, comes with it.

For a plumber, the work is mostly a square line across a stud or joist before you bore it. At 7 inches, the S0101 spans the 3-1/2 inch face of a 2x4 and the 5-1/2 inch face of a 2x6 in one line. On a 7-1/4 inch 2x8 you'll need two passes, and the Big 12 is the better tool for that.

It weighs 0.68 pounds, more than the composite Speedlite but light enough for the pouch. What it doesn't have is a magnet or a guide for round stock. If you work on steel pipe, the Johnson adds magnets. If you mark centers on pipe, the Speedlite adds a center-line guide.

The Big 12 is Swanson's 12 inch Speed Square, built the same way as the S0101: heavy-gauge aluminum alloy, CNC machined to a 45° and 90° corner, with a matte finish. The difference is reach, and that's the reason a plumber would buy it.

Floor joists are where plumbers bore the biggest holes. A 2x10 has a 9-1/4 inch face and a 2x12 has an 11-1/4 inch face. A 7 inch square can't draw a line across either in one pass. The Big 12 can, so the line for a 3 inch drain hole is straight from top edge to bottom edge.

That full-depth line also makes the code check easier. The joist limits further down the page measure from the top and bottom edges. With one line across the whole face, you can mark the center, the 2 inch edge distances and the hole size on the same line.

The Layout Bar is the extra part. Swanson describes it as an aluminum bar that hooks onto the square head and slides along the body. It marks parallel lines without a chalk box, extends past the 12 inch reach for long layouts, and measures the offset on out-of-square corners.

The graduations add an inch ruler in 1/8 inch markings to the degree, common rafter and hip/valley scales. That ruler is handy for marking a hole center a set distance from the top of a joist without reaching for a tape.

Weight is the trade-off. Swanson's page lists both 1.05 pounds and 1.2 pounds for it, and either way it's the heaviest square here. At 12 inches it's also too big to work inside a narrow stud bay. I'd keep it in the truck and carry a 7 inch square on the belt.

Like the S0101, it's made in Frankfort, Illinois, and comes with Swanson's Blue Book. It has no magnet and no center-line guide.

The Speedlite is Swanson's composite Speed Square, 8 inches on a side and 0.28 pounds. It's molded from what Swanson calls a high-impact engineering composite, in Hi-Viz Orange or Matte Gray. The orange one is the one linked here.

The feature that makes it useful to a plumber is the center-line guide. The listing describes a C/L guide for locating the center of round stock. On pipe, dowel or a round post, that gives you a center line to mark from instead of eyeballing it.

The second reason is weight. At 0.28 pounds, it's well under half the 0.68 pound S0101. If your pouch already carries a tape, a level and a marker, the composite square is the one you'll forget is there.

Swanson says the composite glides on soft finishes without leaving scuffs, and that aluminum or steel squares can leave dark marks. That's worth knowing when you mark a cut-out on the back of a finished vanity or a painted access panel.

The markings are molded into the composite, not printed on, according to Swanson. The edge is beveled for easier reading, and the 1/8 inch spaced notches let you scribe lines at close spacing. Swanson says the Speedlite keeps all five functions of the original square.

The 8 inch size gives an inch more reach than the 7 inch squares. Swanson sizes it for 8 inch siding, but for a plumber it means a 2x8's 7-1/4 inch face fits under one line.

What I'd weigh against it: Swanson doesn't list a heel size for the Speedlite, and composite is a different material from the machined aluminum body of the S0101. For guiding a circular saw through framing, I'd take the aluminum square. For marking centers and finished work, I'd take this one.

The Johnson 1959-0700 is a 7 inch aluminum square with magnets in its edge. Johnson says the magnets are strong enough for hands-free use, and that the magnetic edge attaches to ferrous metal. That's the reason it's on a plumber's list.

Ferrous means iron or steel. Black steel gas pipe, galvanized pipe, steel strut channel and many hanger parts are steel. Set the square on a length of strut and it stays put while you mark a cut line, so one hand holds the marker and the other holds the work.

Johnson also writes it up for setting and checking squares before or after welding, and for measuring angles. For a plumber, the same use is checking that a bracket or a strut cut is at 90° before you hang pipe from it.

The body is aluminum with CNC machined edges, which Johnson says are for greater accuracy and durability. The markings are EZ Read laser etching, which Johnson says reduces glare outdoors. The listing adds an anti-glare coating that also adds friction to help the square grip lumber as a saw guide.

The notches are laid out for framing. There are continuous scribing notches for ripping, notches at 3-1/2 and 5-1/2 inches, and marks for 2x4 dimensions at 1-1/2, 3 and 3-1/2 inches. Those match the actual sizes of a 2x4 and a 2x6.

Johnson backs it with a Limited Lifetime Warranty. The model is sold without a printed manual; Johnson posts the full instruction manual on its website.

Two things to know. Magnets don't hold on copper, brass, PEX or PVC, so on a copper job this is a plain 7 inch square. Johnson also doesn't list a weight. The listing linked here was in stock from a third-party seller on the day of the update it, not from Amazon.com.

The Klein 9357SSQ is a 7 inch aluminum rafter square with one feature aimed straight at plumbers: a pipe prop. Klein's own words are that you feed metal or plastic pipe through the pipe prop to cut pipe on the job.

That's the reason it's on this list. Cutting PVC or ABS on the floor of a basement, the pipe rolls. A square that holds the pipe still and gives you a straight edge to cut against does two jobs at once. None of the other squares here lists that.

The heel is 1-1/8 inches, the widest listed on this page. Klein says the heel edge gives stability when you hold it against or slide it across wood or other materials. A wider heel gives more contact with the board edge when you use it as a saw fence.

The markings are double laser etched for visibility, even in sunlight, according to Klein. There's a preset angle guide from 0° to 90°. The 1/4 inch scribe notches are large enough to hold a carpenter pencil, so you can draw evenly spaced lines off the board edge.

The body is anodized aluminum in orange, which Klein says resists corrosion. It's 7.29 by 7.25 by 1.13 inches and weighs 7.84 ounces, or about 0.49 pounds, so it sits between the Speedlite and the S0101.

Where it differs from the Swanson is the markings. Klein's are laser etched on the surface. Swanson's are recessed into the body and filled with black, and Swanson argues those last longer. Klein doesn't publish a test either way, so I'd treat that as a difference in method, not a proven gap.

It has no magnet and no center-line guide. Klein also sells a two-piece kit, model 93547SQVP, with a 4-1/2 inch and a 7 inch square, if you want a small square for tight spots.