I searched online for round caps to sit on top of the exposed pointy knobs of my radiators, but could only find angular ones which were also rather unattractive. So I decided to make them myself.

The design is very minimalistic and requires only a rubber washer to secure the cap onto the radiator knob (see post-printing for details).

Since I don't own a printer (yet :-), I had the excellent Crash from 3D Hubs (https://www.3dhubs.com/service/kresimir) print the caps for me on his Ultimaker. On his good advice, we used Colorfabb Copolyester HT (http://ht.colorfabb.com/) to make sure the caps can withstand the radiators' high temperatures.