It is very difficult to tell from pictures--but the work required to put in the bottom of this "window buck" is enormous. We dig the clay from our property. Sift through rock. Put it together with straw and make Cob (two batches for this window--and also finishing the rest of the wall to make it ready for strawbale). All told, it took us four hours to put in this bottom board to what will be one of our bedroom windows.