Combination Square Hack: This Is the Secret to Perfectly Straight Lines for Your Next DIY

One simple adjustment to true up your combination square makes a world of difference in getting the sharpest, straightest lines while woodworking.

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Every handyman knows that a combination square is a vital tool for drawing precise lines in DIY projects. But even the steadiest hand slips sometimes and the combo square falls off track, leaving you with a wonky line and inaccurate measurements. That’s where a good tool hack comes in handy and, luckily, Tiktok creator @sedgetool has the perfect fix.

@sedgetool Combination Square Hack! #combinationsquare #tipsandtricks #carpentry #woodworking #woodworkingtools #toolhack #howto #pencillines ♬ original sound – Sedge

What’s the Hack for Drawing Straight Lines?

When you’re pressing a combo square along a piece of wood and pressing a pencil into the combo square, it’s easy for those competing pressures to yield shaky lines. To help steady the pencil, this hack helps by creating a small notch at the end of the ruler in the combo square. Then, the pencil and square glide smoothly together down the wood as you draw a perfectly straight line.

To create the notch, take apart your combo square so you are holding the ruler. Stabilize it between two pieces of wood and/or a clamp, so that the short end closest to the 1″ mark is exposed.

Use the long edge of a steel bar stock to saw a notch into the middle of the ruler’s edge. It does not need to be very deep, just enough to comfortably support the tip of your pencil.

Unclamp the ruler, then lap the notched side of the ruler against an abrasive surface to knock off any burrs. Reassemble the combo square with the notched side of the ruler facing upwards, nestle your pencil tip into the notch and draw a straight line on the first try.

What Other Hacks Should I Know?

Now that you’re on a combo square kick, feel free to soup it up with pre-set holes for cabinet knobs and pulls. Or, if you have a speed square, check out these 10 hacks for everything from marking angles to leveling to measuring saw blades. Better yet, why not hack everything in your house? We all could use a helpful home tip or two.

Van Van Cleave
Van Van Cleave (they/them) is a California-based journalist, environmentalist, and artist. A graduate of Brown and Oxford Universities, they specialize in environmental news coverage and sustainable home and garden solutions. When they're not writing, they are typically tending to their plants or experimenting with home design trends.