This design is a box to securely send glass slide samples by post. It uses foam to insure the samples are well maintained and 6M3 bolts to close the lid.
There is a clearance of 6mm that i use to put about 6mm of foam on the bottom and 2mm of foam on the top.
I designed this box for slide thirds (2525mm square slides, 25 slides) but you can also find the files for complete slides (75*25mm, 10 slides).