If the phoenix contact ST1.5 terminal blocks (Reihenklemme in German) get mounted to a DIN rail they will leaye one side open. To protect against touching an endcap is needed.
Sure you could buy them. But you could also print them. If you are worried about fire then you could also print them in flame retardand filament. For industrial use this is probably not the best solution but for privat use (in a printer) it will definitly work.
Printing:
Printed in ABS and PA. Other filaments are not tested yet.
The author hasn't provided the model origin yet.