Sponge can for kids blackboard (Schwammdose fuer Kindertafel)

I have designed this sponge can because the one came with the blackboard of my son broken.

The can is for the sponge it will be hold by the sharp edges. The cover is screwed together with the can that the sponge will not dry out.

In my pictures you can see how it is used.
STEP file is provided!

---------------------------------

German Version (Deutsche Version)

Ich hab diese Schwammdose entworfen, weil der Deckel von der ursprünglichen Version welche mit der Tafel zusammen kam, k