SHF-inspired clamp for linear rails

A parametric SHF-inspired (read: not accurate for milling etc.) rod / linear rail holder for printing. Designed to be a prototyping placement aid, not a mechanically robust part. Use with clamping screws to fasten to panel, and Allen head bolt + hex nut for rod clamping.

Part of the Tannerino project (slide Theremin). See https://hackaday.io/project/133879-tannerino.

Update June 11th, 2018: Changed clamping bolt from d to r, slot was twice as small as it should have been. Changed keyhole t