I just wanted to experiment with a modular shape to snap together into interesting sculptures, so I made a 5x5 square of cardboard with a 1x0.16 piece taken out on all four sides (I also made smaller 4x4 squares to add on to the structure). I had measured the thickness of the cardboard at around 0.16 inches, and after making the original holes 0.17 inches wide I saw that I needed to reduce the space a little. The pieces are still a little lose, but it's fairly sturdy.
I'm going to work on using pieces like this out of wood to build a kind of cubicle wall, but I need more time to experiment with it.
Corel Draw File