I’m sure a lot of Toolmongers already know what this is and what it’s for. But a friend who found one of these in a toolbox he bought asked me what it was, so I thought I’d share here as well, just in case. I’ve always heard it called the “try square,” which my father told me was due to the fact that “trying” is kind of a work-slang for checking something to see if it’s straight. But it seems others call it a “tri-square” as well.
A quick run to Wikipedia suggests that this might “refer to the three purposes of this tool: 1. To check squareness, 2. To check flatness, and 3. to lay out lines.” Ok — that’s certainly what I do with it, but it never occurred to me to call it a “tri” square. Can any of you old-timers (or high-timers, either way) confirm this?
The one linked (and pictured) above is from Irwin and looks pretty nice, featuring a hardwood handle. Super nice ones will often feature brass rivets or rare woods, though all it really needs to do is be straight to do its job. Mine sees a lot of use marking steel for cuts in the shop as it’s easy to slap it on a piece of tubing and draw a nice, straight 90-degree line. I use the ruler markings to mark tubing cuts for closures, too.
So what do you do with yours?
Hardwood Tri-Squares [Irwin]