If you are designing a box to be cut on a laser cutter you are faced with the problem of how to join to perpendicular faces together. You could press fit your parts together. You could use snaps to hold your mortise and tenon's together. You could use a captive nut on the mortise side and thread a screw through the tennon side. ect ect
I hope to show you how to make a brand new joint which is simple and strong.
The mortise and tenon joint is at least as old as the pyramids we think this because we found a ship that uses them in one of the pyramids. http://en.wikipedia.org/wiki/Mortise_and_tenon
In this variation of the mortise and tenon joint, we add an extra feature which allows us to thread in a screw fastener which works to synch it all together. It is a simple modification which makes for speedy construction.
This joint works great for cnc fabrication such as laser cutting, cnc routing, water jet cutting.
Designing a mortis and tenon is straight forward. Measure you material. Make the mortis and long as the material is thick and make the width of your tenon the same as the material thickness. Then at the end of the mortise slot add a circular hole. The hole should be the size of tap drill for a common screw. I recommend using the screw which is as close to the material thickness as possible. Place the whole so that it only overlaps with the space for the mortise by .5mm.