Miter Gauge Sled & Box-Joint Jig
The blade setup determines how wide and deep the pins and sockets are on your joint. Box joints look best when they are cut to match the thickness of your stock.
Make a test joint before cutting into the material you plan to use for your box. You'll likely have to fine-tune the position of the plate.
Check that the blade is 90 degrees to the tabletop and 90 degrees to the miter gauge fence.
If the joint is too loose, the pins are too small; increase the space between the blade and the key.
If the joint is too tight, make the pins smaller by sliding the key closer to the blade.
Fence Plate Miter gauges screwed to fence Key 1/2"