Simple Advent Calendar

This is a simple advent calendar, fairly quick to print.

Tolerances can be nasty though... I therefore suggest that you start by printing the frame, and then print one box. Make sure the box fits perfectly in the given slot; if it doesn't alter the dimensions ever so slightly. The boxes are made to fit perfectly on my printer, but unless you break into my home you are unlikely to print on my printer.

An important note, the tolerances are slightly different if you turn the frame 180 degrees since the thing holding the boxes in place gets a different surface to push on, so try doing that first after printing your test box.

Edit:
I added a hold in place thingy. Se image for how it is used.