These are simple springy legs I designed to hold up some agate slices so sunlight could pass through them. They should also work for other thin (1/8" to 1/4") slabs you want to display - pictures on plywood, e.g. Note that the contact points don't fully close, so they won't hold anything thinner than about 1/8". They do provide a bit of pinch, so might not be suitable for material that can be easily dented (soft foamboard or the like). There are two models provided, differing in their springiness - I used the strong variant (the black legs in the pictures) for a heavier agate slice and the light variant for a smaller slice. FreeCAD models are provided so you can adjust these if you like to provide even stronger or lighter versions. I printed these at 0.8 scale in ABS for the legs in the pictures.
I printed these at 0.8 scale in ABS for the legs in the pictures.