Portable computer projectors have an adjustable foot (screw) for elevation. They're always either not high enough, or broken, or both. This leads to a scramble to find some way of tilting up the projector. A stack of these disks does an excellent job. They're small, so they'll fit into the projector's carrying case, they interlock, so that the ones in the middle won't slip out, and the top one will have an indentation for the existing projector foot to fit into.
I've provided 3 different sizes, approximately 8mm thick, 4mm thick, and 2mm thick. Having 6 of the 8mm, 2 of the 4mm, and 2 of the 2mm makes for a good choice.
Caution: Do NOT use PLA for these. PLA gets soft at about 50C (122F), and some projectors get hotter than that, plus it's easy to reach those temperatures in a closed car in the summer (especially here in the Phoenix area).
Do NOT use PLA to print these! Some projectors vent hot air where it will cause the disks to get hot, plus they can get hot in a car in a parking lot. PLA can get soft and have nasty things happen, but ABS won't.
I have given several sets to clubs I'm in. I usually put 6 each of the 8mm disks, 2 each of the 4mm disks, and 2 each of the 2mm disks. This allows a good range of adjustments. I'd be inclined to put more, rather than fewer, in the sets. They're not heavy, nor do they take up a lot of space.
I used FreeCAD 0.14, and included the .FCStd files from FreeCAD in case someone wants to modify them.
Note that they don't perfectly interlock, so there does appear to be a gap, but that's OK.
I've been printing them at 15% fill (the Cura default), and that seems to work fine. If you want to use them for something heavier, you might need to go to a higher fill.