Reuleaux Triangle

That solid is of constant width.
It will roll between two parallel planes.

Print with no supports
reuleaux_triangle_top.stl , bottom and plug. flat face down.

Cut in 2 halves for cleaner print. With a plug for connection.

If you have a little elephant footing on the plug, good. Push the plug foot first in one side. It will lock. Don't really need glue. It seems to hold as is.