TOH Tested: Combination Squares
The most versatile layout tool going will mark lines, measure thickness, check for square, and much more
Look past its gangly appearance and meet the most versatile layout tool going: the combination square. It'll mark lines, measure thickness, check for square, and much more. Click through to see the five that deserve a spot in our toolbox—from heirloom-quality to bargain-bin.
What to look for:
1. A blade with easy-to-read markings.
2. A pleasantly hefty square head, preferably cast iron or forged steel.
3. A knurled adjustment knob to lock or loosen the blade.
4. A scratch awl at least 1 inch long that fits snugly into the head.
5. Nicely machined edges free of pitting or paint.
Price: About $30; johnsonlevel.com
At roughly one-quarter the price of an heirloom-quality combo square, this cast-iron workhorse, with a nonreflective finish, is the very best of the home-center fare. We like the threaded awl and easy-to-read green leveling vial but wish the sides of the head were better machined. It could also use a more prominent adjustment knob.
Price: About $8; empirelevel.com
This 6-inch-long pocketable square is easier to use for checking small parts or setting router-bit heights. The bright blue vial is a snap to read. Twist the chunky knob to loosen the square lock bolt, which can't spin freely, and easily adjust the blade. The chamfered edges on the head make it comfortable to hold.
Price: About $7; swansontoolco.com
Consider this the equivalent of a beater chisel, except with some nice touches—like a knurled brass knob—you wouldn't expect to find on a sub-$7 tool. The readable blade and large vial are nice touches. And even though the head is plastic, it comes with a threaded awl that rests proud of the head—easy to grab.
Price: About $36; lagesseproducts.com
At 2 inches wide, the aluminum head of this square won't tip when you're marking pipes and tubing. It's also great for trueing a table-saw blade or checking an inside corner for square. That said, this isn't the choice for marking 1× or other thin stock, since you'd have to prop up the material to meet the blade.
Price: About $100; starrett.com
Nice to see that the company that introduced the combo square, in 1877, still makes one of the best. The forged-and-hardened steel head is paired with a blade etched with gradations filled with paint. A satin finish renders them easy to read even under the glare of your shop light.
With a tool prized for its accuracy, it's worth checking every now and then to make sure yours is true.
Extend the blade as far as possible, grooved side up, through the 90-degree face of the head, and hook the square against the straight edge of a board. Scribe a line along the blade. Now flip the tool over, groove down, and line up the same edge of the blade with your mark. If they're parallel, the tool is square. If not, it needs to be repaired or replaced.
Set the blade to the notch's depth. Hug the square to the board and, holding a pencil against the end of the blade, drag both along the board to mark the base of the notch. Use the blade's long edges to mark the width. To check the depth of your cuts, position the square as shown, bottom out the blade, tighten the knob, and read the marking.
1. Draw a line across the board 90 degrees to both edges.
2. Use the 45-degree face to draw a line from the point where the 90-degree line meets an edge of the board.
3. Flip the square over to the board's other edge and draw another diagonal, as shown, from the opposite end of the 90-degree line. Where the diagonals intersect is the centerline.
Unplug your circular saw or remove its battery, and flip it upside down. Place the square's 90-degree face against the narrow edge of the shoe and extend the square's blade until it touches one tooth, as shown, then tighten the knob. Read the marking and clamp a straightedge at that distance from your cutline on the keeper side. Cut away.