What are battens?
A batten is another type of bracing that is used to secure all of the edges of the box. It is a thin piece of wood that runs along the joints of the box, as seen on the left. You can usually get strips of wood in 1″ x 1″ or 3/4″ x 3/4″ sizes in either pine or hard woods. The batten does not need to run the entire length of the edge. It is fine to cover 2/3 of the edge with the batten. Screw the batten into both sides of the box, making sure that you don’t hit another screw. It is not necessary to countersink these screws. You should use a #6 1 1/4″ screw for the batten, which will allow the screw to go deep enough into the MDF without coming out the other side. Again, pre-drill the hole and use plenty of wood glue.
