By precisely measuring 45- and 90-degree angles, the combination square is often called upon to create miter joints in addition to marking lines, measuring thickness, checking for square, and making other measurements. For instance, combination squares can be used to check the depth of cuts or to assure the straightness of the blade on a circular saw. To make sure that the combination square itself is square, extend its blade as far as possible and scribe a 90-degree angle along the blade. Then flip the tool over and scribe another line which should be perfectly parallel.

“Measure twice, cut once” applies to every aspect of a project, angles as well as length. We have all the tools you’ll need to make sure you are plumb, straight, and true, from combination squares to measuring tapes to levels.

HINT: A quality combination square has a blade with easy-to-read markings and a cast-iron head of forged steel.