The SBB acquired over 1000 open goods wagons of the L6 design between 1918 and 1923. They were initially used for the transport of coal, but also for other weather-sensitive goods. The L6 wagons were built with wooden and steel walls, as well as with and without a brake van. Based on the L6, the SBB procured wagons with raised side walls for the transport of logs and scrap metal. A total of 318 wagons classified as Fbkk were built.