Cut custom grooves

Next, cut the grooves that receive the plywood panels and tenon tongues along the inside edges of all the pieces. The width of the grooves must match the thickness of your plywood. You’ll accomplish this by making multiple passes, widening the groove a little each time until it’s just right. It doesn’t matter if you have a thin-kerf or standard blade—either will work. Start by drawing a center line on the end of one of your test pieces. Place this piece on your saw, then adjust the saw’s fence so that the blade is positioned slightly off the line. Next, adjust the height of the blade to cut a bit more than 1/4 in. deep. (Halfway between 1/4 in. and 5/16 in. is about right.) Saw a groove

Always use a featherboard to hold the wood tight to the fence as you push.

Next, flip the board end for end and make a second cut

This widens the groove. Check the groove’s depth and adjust your blade up or down if necessary. See if your panel fits. The panel should slide into the groove without requiring any force, but it shouldn’t wiggle, either. If the groove is too narrow (and it probably will be on the first try), nudge your saw’s fence a tiny bit and repeat both cuts. If the groove is too wide, adjust the fence and start a new groove on the other side of the test piece. When you have the fence setting just right, cut grooves in all the rails and stiles.

(Photo 4). (Photo 5).