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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]


21 Responses to The Try Square

  1. Simon says:

    I bought a folding square from Sweden 20 years ago because it looked cool. Now after all that time it is still perfectly square since you can bump it around and store it in a tool bag easily. It has spring loaded ball bearings which seat into holes which even if they did wear, would still be accurate.

    As a bonus it has a 45′ setting also.


    • Robert says:

      I love Lee Valley & veritas stuff.

      The LOML says it is tool porn when I look at their website!

      I’m always amazed at how fast I get stuff from a Canadian store. Do they have Warehouses in NY?

  2. Steve says:

    I’ve always just called it a square. I somtimes use a framing square. I usually reach for a combination square which can mark 90 and 45 degree angles. The combination square can also be used as a depth gauge and a marking gauge by sliding the scale in the head.

  3. fred says:

    Lots of squares out there. The one pictured is a “try square” – as in checking or “trying” for squareness as in case work / woodworking.

  4. Old Tool Guy says:

    I have my Grandfather’s tri square, as well as one of my father’s. For some reason, they must be worn out because it seems that both of my long-passed ancestors were able to measure and cut much more accurately than I ever have been able to when using them…

    But in any event, I always understood it to be a “tri square” because it was formed by two sides of a triangle.

  5. o1d_dude says:

    I’ve always called it a “try square” for the reasons stated above. When made completely out of metal, these are sometimes called “engineer squares” and are used to set up adjustable equipment such as table saw blades and such.

    It’s definitely a square, tho, regardless of what other modifiers or descriptors we attach to it.

  6. rg says:

    To verify if your square is “square”, all you need to do is put it on a piece of material with a straight edge.

    Lightly draw or scribe a line along your square, perpendicular to the straight edge on your material.

    Now flip your square over, and scribe another line in the exact same spot.

    If the 2 lines you scribed are converging/diverging or crossing, your square is not 90 degrees. If your square is good, you should only see one line.

    You can use the same principle to check if your mitre or table saw blade is set perfectly for 90 degrees. Cut a peice of scrap; place the resulting two pieces on a flat surface (like your clean table saw top), mate-up your cut line. Now flip over on peice and try to mate up your cut line. If the blade was set perfectly, peices should mate perfectly along the cut line — otherwise you’ll see a ‘v’-shaped gap. The longer the cut line, the more accurately you’ll be able to test.

  7. Brad Justinen says:

    Star Trek, Star Track, only one is right. Calling this a “try” is simple wrong even if the name (and story) were handed down for generations. It’s call a Tri(3) square because it does more than just check for square(2).

  8. JKB says:

    I have a scan of a book, ‘Woodworking for Beginners’ by C.G. Wheeler. The imprint is missing but the preface is dated June 1899.

    The book has very good explanations and detailed use instructions on lots of tools and methods. For the try-square it states:

    “The primary use of this tool is to test or “try” the accuracy of right-angle work – hence the name.

  9. don daso says:

    Fifty years ago, in shop class, I was told it was, indeed, a “tri-square,” because it did three basic measurements. The school shop had 20 of them, all exactly alike, all metal construction, mounted on the pegboard wall. It was a handy tool, especially for young, inexperienced hands trying to make things from wood. Making them square, level, & precise…well, the square went a long way in helping us with that.

    My shop version today has a wooden handle (it’s at least 20 years old), & is used almost exclusively in metal working (antennas, mostly). Quite simply an indispensable tool to ensure those same three basic
    measurements are accurate.

  10. metis says:

    as stated above, it’s a try square because it’s used to test for square. there are many more than three tasks one can do with this tool, so “tri” is at best a poor misunderstanding of the tool and a retronym.

    in metal, it’s called an engineers square, and from what i’ve seen of *old* wood working and metal working squares, i suspect it’s a low cost, lower accuracy version made for woodworking, where accuracy to a hundredth of a degree isn’t as critical due to the inherent compressibility of the material.

  11. fred says:

    BTW – there is also a “try” or “trying” plane = sometimes associated with a jointer plane like a No.7 – but also sometimes the name is given to a shorter plane more like a ‘fore plane (No.6)

    • Jason says:

      Fred beat me to it.

      Boards were said to be “tried and true” when they were flat and square after being worked with the try plane. To judge the accuracy of the work, a “try square” was used, hence the name.

      “Tri square” is yet another erroneous “fact” passed down through shop classes.

  12. Brian Dolge says:

    Tri, Try… getta life. On the other hand, varient features make a difference. I have on that has the wood section beveled so that it can also be used to check 45 degree angles AND can be used with a straight edge to funtion as a center finder. Often simple little changes can increase a tools usefulness in huge and unexpected ways.

  13. sander says:

    I use it for making sure the blade on my table saw, circular saw, or jigsaw is perfectly square to the base of the saw. I’ve also used it for marking 90 degree lines on boards before cutting, but I usually reach for my combination square for that.

  14. ChrisW says:

    Perhaps we should spell it TRU square as a compromise. I just wish I had one. I make do with newer design multi-purpose squares but I like the looks of a Try Square.

  15. Spyros says:

    You are wasting too much time in the precise name of this tool while none noticed that in both pictures the instrument is misused. You should always draw the line from the inside, therefore despite the pencil’s pressure the line is always straight. Otherwise, drawing the line from the outside (like the pictures above) the line could sometimes be curved . Just try it out!

  16. Bill Kaline says:

    Call it a TRY or TRI square, it is primarily a tool for checking the square, or flatness of wood, or metal. The Egyptians are credited with inventing the first one, and there are numerous patents for improving this simple tool going back a hundred plus years. Those squares using the Winterbottom patented improvement are designed to also make 45 degree angles. The early squares had hardened and tempered steel blades and a brass faced rosewood stock. Lines were scored using a common scribing, marking or striking tool. Engineer squares are made of all metal.

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