How a Combination Square Changed My Weekend Projects

For the first twenty-some years I built things in that garage, my marking tools were whatever sat on the rack at the hardware store. A short plastic speed square. A folding rule. A carpenter's pencil I sharpened down to a nub with a utility knife. It was fine for a step stool, and for a lot of years a step stool was most of what I built.

Then my daughter asked for a blanket chest, and the lid had to sit flush and the corners of the box had to be square, because a box that is out of square racks the minute you put clamp pressure on it. I found out in a hurry that a speed square was giving me a suggestion, not an answer.

So about four years ago I bought an IRWIN 12 inch combination square. Metal body, stainless steel blade, black precision-etched scales graduated down to 1/16 inch, and a head marked for both 90 degree and 45 degree work. It hangs on the pegboard next to the pull saw now. It comes off that hook more often than any other tool I own.

What that gets you that a speed square does not is a tool that slides and locks. The head travels the length of the blade and tightens down where you put it. So the same square marks a cut line, checks a corner, and sets a depth off the edge of a board. Three jobs, one hook on the wall.

The depth part is what I did not expect to use so much. Mark a hinge mortise, flip the square, mark the shoulder on a tenon. Two moves instead of five, and no walking back to the bench to hunt for a second tool with a pencil already in my teeth.

The head slides and locks, so one tool marks the cut line, checks the corner and sets the depth. I stopped walking back to the bench for a second tool.

Where it earned its keep was glue-ups. When you have a frame in clamps and you are not sure whether you pulled it out of square with the clamp pressure, you put the head against one side and look at the blade against the other. Light under the blade, or no light, tells you what you need to know. I have taken a picture frame apart and reset it more than once because of that check, and I would rather do it before the glue sets than after.

The 45 degree side of the head is the other half of the story. Picture frame miters are where I used to fudge. Now I mark the miter, cut it, and check the cut against the 45 side before it goes anywhere near glue. Frames close at the corners now. Not because my sawing got better, but because I finally started checking.

Cutting boards are the other place it shows up. When you glue up a board and the ends are not square, the whole thing sits crooked on the counter and you see it every single time you slice an onion. I check the ends with the square before the final glue-up now, and I have not had one rock on me since.

The bookshelf I built for my youngest grandchild is where the gauge side of it showed up. I set the head to the depth I wanted, laid the blade across the workpiece, and marked a line at a consistent distance from the edge all the way down both sides. Same setting for every shelf. That is the difference between a shelf that looks handmade and a shelf that looks home made, and those two are not the same thing.

Now the honest part. The IRWIN blade is 12 inches. Anything wider than that and I am using a different tool, which is why the folding rule still lives in the drawer. The graduations stop at 1/16 inch, so for finer layout I use a marking knife and a straightedge. The head is metal and the whole thing runs 14.4 ounces, which feels solid on the bench and would feel like a paperweight on a ladder. And it is a precision tool. It does not like being dropped on a concrete floor.

I dropped mine once, straight off the bench onto the slab. The first thing I did was check it against the factory edge of the bench top and against a corner I already trust. It was still reading square. If it had not been, it carries a limited lifetime warranty and I would have made the call. A square that is out by a degree is worse than no square at all, because it lies to you quietly on every project and you blame your saw work.

What I'd Tell You If We Were Sitting at My Kitchen Table

I would tell you that most of the tools in my shop did not change how the work comes out. They changed how long it takes and how much I swear under my breath. This one did both. It is not a fancy tool. It is a plain metal square with a good blade and a head that locks where you put it, and it earns its spot on that pegboard every single week.

And I would tell you to get the 12 inch version and not the small one. The short one is handy in a drawer, but the 12 inch blade is what spans a picture frame and reaches across the diagonal of a blanket chest lid. If you are going to own one, own the one that covers the work you actually do. If you are still deciding between this and the sheet metal square in your toolbox, I have written about that trade separately.