Bahtinov masks are easy to 3dprint, and are a very precise focus tool when preparing an astrophotography session. Grid holes in the mask cause diffraction spikes to appear when looking at the point light from stars. Achieving optimal focus consists in centering the middle spike between the side spikes, so that the figure is symmetric.
I’m prototyping telescope piers with 3dprinting. Usual discussion over rat cage and fixed plate… Then, wood, metal or concrete implementation.