Building the box jig
To cut box joints, start by building a jig for your table saw. First, cut all your parts to size, including trimming the 1/2-in. square key stock, and then change your table saw blade to a 1/2-in. dado stack ( Photo
1). With the miter gauges in the miter slots, fasten the fence through the back of the miter gauges with 1-1/4-in. screws to make a sled. Clamp the plate flat against the fence and push this setup through the dado blade. Unclamp the plate and glue a 3-in. length of 1/2-in. square stock into the cut you just made. Create a space between the key and the blade using the remainder of the 1/2-in. stock; this makes the pins and sockets the same size ( Photo
2). Clamp the plate to the fence.