If you are a Software Carpentries (https://carpentries.org) instructor you will be familiar with the use of sticky notes by learners, red to indicate that they need help and green when they are okay or have finished an exercise. My problems has been that the stickies don't stick, they keep falling off the screen. So I came up with the idea of printing two discs, one with a cross (in red) and one with a tick (in green) that can be mounted on a kebab stick and Blu Tacked to the side of the monitor. Although red and green are used, these signs are usable by people with colour vision deficiencies as the icons and the colour contrast are clearly distinguishable from one another. I tried it in a workshop and it worked very well.
I don't have an MMU so I sliced the discs to stop for a change of colour when it gets to the cross/tick. I printed them with a 100% to give them a bit of weight. I think they're too thin for a fill anyway. Two discs are glued together, back-to back, so that you will have a cross or a tick on both sides and a little “tube” into which you can push the kebab stick.
2024/12/13: I have added two stl and two scad files for printing little stands.
The author marked this model as their own original creation.