My cat is huge and bent the thin rod that props up the greenhouse lids. I could bend back the rod, but it may not help for long. So, I've designed this wedge for each side of the greenhouse to prop the lids to let the plants breath a bit.
Print how you'd like. The one pictured is set to .25mm layer height, 5% infill, and no shells. It could use more infill and shells if I want it to really stand up to my cat standing on the lid of the greenhouse.
I may be adjusting the degree of the angle and also the height.