I was reading John Kramme's post about making his own boxes, and was reminded about a tip I picked up a little while back that helped me. I found a woodworker's post on Youtube (Charles Neil Woodworking/Gluing A Mitered Box), that helped me with an upgrade to some of my builds. The video shows a method of using painter's tape/masking tape to glue and clamp a mitered-corner box. I have been making butt joint boxes for my license plate guitar builds. Strong enough for git builds, but not as pretty as a nice mitered corner.  I just couldn't seem to clamp mitered corners worth a darn. Strap clamps, spring clamps, pony clamps, corner clamps...just was never happy with my results. Anyway, here's the bottom line - Cutting close 45* corners, laying the pieces out with the tape (as shown in the video) using glue to seal the end-grain joints before doing the final gluing/assembling, and brothers and sisters, a neat clean miter glue joint can be had by the likes of me, an amateur woodworkin' git builder. Helped me, maybe it will help some of you. Not magic, but easy and cool.