In times of war the task of the WPB („War Production Board“) was to allocate resources wisely, so that an effective armaments production could be established and maintained. Saving rubber was one of those tasks, which is why the footboards of military and civilian machines from 1943-1947 were equipped with metal mats instead of rubber. WPB boards are correct for the mentioned year group, but basically fit all 4-speed Big Twins and 45cui models 1940-1984.