The roof plates (top plates) need to be uniform in size and strength. The most common method uses the wooden-ladder style of plate which is made up of two pieces of 6 x 2 on edge: one that runs along the inside edge at the top of the bale wall, and the other that runs along the outside edge. These 6 x 2s are fixed to a piece of 18 mm plywood 350-450 mm wide. Six-by-two noggins are required every 1800 mm to give stability. We also put in 4 x 2 noggins every 900 mm between the threaded rod to assist with fixing the roof trusses. The 6 x 2 noggins also correspond to the location of the continuous thread that connects the top plates to the foundations, as described in the Foundations section.