Hello! The bamboo mat ceiling is hung flat by keel, and no additional measures are needed for leveling. On the back of the mat, corresponding to the transverse keel, a thick and hard layer of canvas, linen, non-woven fabric and other cloth strips is glued, and then nailed to the keel. If the requirements are higher, it will take a long time. Glue the cloth strip to the keel, and then nail it to the keel on the surface.