These squares can be useful for people who don't need a high level of accuracy or building smaller projects. If you're working with 1/2 inch plywood that's already semi-warped from one of the big department stores and you plan on just twisting everything together, that would be perfectly acceptable. absolutely correct with this construction). Squareness so my mortise and tenon joints line up properly. Notes on Accuracy. When I placed two of them back to back, the top pieces visually touched, but I could also see a small gap at the bottom, confirming my calculations. If you use these to align your track saw on an 8ft board, you would be off 0.6" at the other end. So if you're doing a small project and only have 1 foot of cut, you'll be off by 0.07456 inches. (5/ 64") Were they cheap enough that I didn't have to return them? I'm on the fence. Maybe my friend can use them better than me. Will I use them to make high end furniture? No. I will most likely save up and buy some woodpecker squares where they post their accuracy.