The fronts of the frames. Made out of 1/4 (I forget the metric equivalent) water resistant luaun. I soaked a piece of this in water for a week to see how it'd hold up. No damage at all. Holes are evenly spaced depending on the height or width of the frame. On these they are between 2.5" (horizontal) and 2.7" (vertical). After all the holes were drilled and dished I painted the fronts with two coats of a high quality exterior latex. No way to paint this after the bulbs are in.