I’ve built quite a few cabinets over the years. And one of the challenges that always comes up is marking a straight line on the inside of the case for partitions or drawer slides. The problem is most store-bought squares are either too long to fit or too short to draw the line I need. The solution I came up with is an adjustable square. It’s simple to build and works great. So well, in fact, that I use it all the time on all kinds of projects.
What makes the square so versatile is its sliding tongue design. As you can see in the photo and drawings, there’s a long slot cut along the length of the tongue. Instead of permanently attaching the tongue to the head, I use a bolt and knob to secure the two together. When I need a shorter square, I simply loosen the knob and slide the head down the length of the tongue. It’s important for the two pieces to remain square to each other. So when fitting the parts for the head, I used the width of the tongue to set the spacing of the head components. Finally, apply a coat of wax between the head and the tongue and you’ll have no problem making adjustments.
