Sarking refers to the process of fitting timber boards or sheets to the rafters or underside of a roof. There are various synonyms one can use for the word sarking, such as roof sheathing, decking, roof decking, or roof substrate. In some places, it is also known as roofing underlayment. Sarking plays a crucial role in providing insulation, support, and durability to the roof structure. It also helps prevent moisture from infiltrating the roof and damaging the building. Depending on the type of building and roofing system, different materials can be used for sarking such as plywood, oriented strand board (OSB), or particleboard.