The roof truss is the supporting framework, the substructure for the roof. With the exception of a flat roof, a roof can be designed as a rafter roof – which is the simplest form of roof design – or as a purlin roof if dormers or large skylights are to be installed. With a SPAX washer head screw, for example, even badly twisted rafters can be tightened. It’s then possible to do without rafter-purlin anchors. The SPAX range includes full and partial thread screws between 8 and 12 mm. And for particularly narrow wood sections, there’s also a 6-mm SPAX washer head screw. The partial thread ensures particularly good tightening of the uppermost layer of wood. These SPAX are available zinc-plated, WIROX-coated or in stainless steel.