Glass block adds a nice decorative touch to earthbag walls. The building process for adding glass block is fairly simple: Make wood frames much like window bucks, only smaller. Earthbag walls are quite thick, so you will probably want double glass blocks – one near the interior, one near the exterior. This creates a wide, strong surface to support earthbags above. To do this, build 2×4 frames (bucks) for each glass block. Plan ahead so you know where to insert the frames in the wall, and then set and level the frames where you want them. Frames are held in place by earthbags pressing against them. Curve the bag ends that adjoin the frames by pinning corners of bags out of the way to create gently rounded edges in the plaster. Set the glass block in place after the walls and roof are finished. Add four nails behind each block to hold in place, and then plaster around the blocks.