How To Square Up Framed Boxes

Any time you're building a project that involves creating a box / square / rectangle type shape out of lumber you run the risk of it not being square. Meaning, it's easy to build a square or rectangle shape that ends up being more of a skewed trapezoid.

So how do you make a square or rectangle shape and ensure that all four corners are perfect 90 degree angles? The first tip to perfection is to make an accurate cut. If you're making 90 degree butt joints or 45 degree miters, you want accurate and smooth cuts so the pieces fit together. That alone will get you most of the way to perfection, so use a miter saw (affiliate link) (they're very affordable!).

Even with a great cut you might be at the mercy of your lumber. 2x4 lumber is often notoriously rough and inaccurate to work with for example. Sometimes it needs a little persuasion to reach 90 degree perfection.

But first you have to know what you're aiming for. To so that, take accurate measurements diagonally across your square / rectangle box. Measure from one corner to the opposite corner. This needs to be accurate so use two people if possible. Have one end of the tape measure hooked on the far corner, right in the middle of the hook. On the other, measure right on the edge of the tape measure where the numbers are. Note the measurement.

Now switch to the other set of diagonal corners, making sure you are setting up the tape measure the same way. Are the two numbers exactly the same? If so, your corners are good. If not, your corners are off. You'll now need to skew your work a little bit (one way or the other) and measure again. Repeat that until both measurements are equal.

Depending on the piece you're working on, it's often helpful to clamp things in place as you do this and then do a final gluing / nailing / screwing to hold it all in place once you've achieved perfection. Want to make things even easier? Then grab a few (four is best) of these awesome 90 Degree Corner Clamps (affiliate link). They're a lifesaver!