My grandson has got a set of the modular system QUADRO, and we soon succeeded in damaging one of the screw keys ;-)
So I designed one to print on my 3D printer with the goal, to minimize the need of support.

Maybe this is a help to anyone too?

You might also be interested in my other parts for the QUADRO system:

• https://www.thingiverse.com/thing:6053610 QUADRO End Cap
• https://www.thingiverse.com/thing:6149122 Schraube fuer Baukastensystem QUADRO
• https://www.thingiverse.com/thing:6149142 Schraube fuer Bretter am System QUADRO