"Glassboard" Marker Holder that just clips on the side of the board and uses friction to hold in place.
Same design as my other Slim Whiteboard Marker Holder (https://www.thingiverse.com/thing:4910723) but for glassboard type of whiteboard it doesn't work. With glassboard the metal sheet is behind the glass so you would need extremely strong magnets. So I designed a clip-on version that doesn't need any magnets.
Designed and tested on a (glass) board that is 4.4mm thick but will probably work with any board from 4 to 5mm.