A holder designed for hobby knives (xacto knives). It has a holder up top that you hold the knives in. The holder takes a small insert of foam core at the bottom - rip the paper off - to keep the tips from snapping if you toss a knife in. Bay below is for holding spare blades.
I've included a box for storing used blades that you can 3d print that will fit in the blade bay.
Cut two of the sides, and one of every other piece.