Tons of calibration cubes around? might as well put one to a use… this is a base for 4.9mm extruder rods which simply presses onto the end to visualise the movement.

Simply superglue your chosen right-angled model into the triangular groove ensuring the cube rotation is correct (XYZ facing outwards).

In your slicer, use the ‘convert round vertical holes to polyholes’ (superslicer, print > slicing) else the round hole will print too small and wont fit. Orientation probably doesnt matter but i rotated so the triangular face was on the print bed. 

Used on the Creality Sprite Pro extruder, with a 15mm^3 cube as the 20mm^3 wont fit due to parts cooling fan. Probably fits others.