These handy, modular clips are designed to hold a sheet of metal or card in order to block any stray beams from your optical table - we used some nice corrugated, black-annodised aluminium. Being able to mix and match allows you to quickly drop in or remove sections of your beam block and split your table into sections without having to install large lengths of material or a gantry around the table. You could also use them as holders for alignment targets. These are designed for metric tables (the design captures an M6 caphead screw) but should also work with imperial tables (and 1/4"-20 caphead screws).

Print a bunch of the different variations - you never know what your experiment may call for in the future... We found that the 3-way and right-angled 2-way pieces are really handy, so print more of those. Drop an M6 (or 1/4"-20) caphead screw into the hole in the top of the mount and use a ball driver to push this through the base and mount to your optical table. Place a few around your table and connect them with some sheets of metal or card.