This is a two-parted, magnetical case to protect a drawing triangle from damage.

The problem with this type of ruler is, that they tends to easy break in the school bag.
The case from the photos was already in use throughout the last school year and not one triangle was broken.

This case is for a drawing triangle (rectangular ruler) with an edge length of maximum 16cm.
The two parts a symetrical and hold together with magnets.
The max. 12 pieces of 5x1mm magnets are simply glued in.

print settings:

I printed it at 0.2mm resolution with Pruament PETG.

bonus:

I also add the 3D model as a step file for your customization, 
e.g. the name of the owner.