There’s not much we could do in the woodshop if we couldn’t make sure things were square. The most popular tool to do that is a combination square, a tool that looks much the same as it did when Laroy S. Starret invented it in 1879. But a new version from Kapro gives that revered tool an upgrade.

The classic combination square has an engraved metal rule, usually 12 inches, with a groove down the center of one side. A machined cast head slides on the rule with a spring-loaded locking knob that uses the groove in the rule to lock the head tight and accurately at 90 degrees to the rule. You can get other heads, but the classic version has a 45-degree angle and a 90-degree angle plus a bubble level and some kind of scribing instrument inserted into the bottom of the head.

A different take

The classic tool has worked great for 140 years, so why change it? Kapro’s idea is to make the tool even more versatile and easy to use, and the secret to that is magnets. The old locking method was sometimes problematic. With use, dirt would get in the groove, the spring would get tired, the locking knob would get hard to turn, and adjusting the head on the rule would become a pain.

Kapro’s version (officially the model 325M) uses powerful magnets to lock the rule in place. That offers a number of advantages. It’s really easy to slide the rule where you want it, but the magnets are strong enough to hold it securely in place for measuring. Making depth measurements by sliding the head on the rule is sure and smooth. You can instantly remove the rule to use separately or to clean to ensure accuracy. And if you accidentally drop the tool, it’s less likely to be damaged since the rule will just be knocked loose.

More than magnets

The rule itself is nicely engraved for easy reading with scales in 16ths and 32nds of an inch as well as millimeters and has precision milled sides. Rather than inserting into a hole at the base, the scribe on this square rides in a protected recess held in by the same magnets that hold the rule in place. While the old-style scribes frequently fell out and were lost, there seems to be less of a chance of that happening with this system. The standard bubble level is easy to read and highly visible.

At less than $25 and available at major home centers and online outlets, the Kapro magnetic lock combination square is a real value and worth checking out. For more information visit


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