If you need to build a sawhorse to exacting dimensions, you need to know exactly how tall it will be when you assemble it. This can be tricky because of the sawhorse's slanted legs. When building a sawhorse, you don't have to use complex geometry to figure out the exact height, just use a mechanical drawing of your sawhorse leg profile. Once its laid out on a flat surface, you can then measure it straight up, and trim the legs to get the perfect height.
Things You'll Need
3/4-inch plywood,48-by-48 inches
Straightedge, 48 inch
Stand the sawhorse beam up vertically, centered on the plywood with the edge of the beam flush with the edge of the plywood. Lay two of the legs out on their sides on the left and right in their angled portions as if they were already attached to the beam.
Lay a straightedge along the bottom of the legs as if the straightedge were the floor.
Hold the straightedge in that position. Remove both legs and the beam and draw a line down the straightedge to represent where the floor would be.
Measure from the top of the plywood to the line for the exact height of the sawhorse.
If your sawhorse legs are too short or too long for your desired height, alter the angle of the legs, or slide them up and down on the side of the beam until you dial in your height. When you get ready to build, put a clamp across the tops of the legs, clamping them tight to the beam. Screw them together with wood screws and glue.