POLY-FAST™ roofing fasteners feature a Thermal Expansion Hole Cutter that creates a much-required thermal expansion hole on plastic profiled roofing panels, The panels are then securely fastened onto the purlin support underneath in onego.

A nominal 11mm diameter hole is created by the Thermal Expansion Hole Cutter during the process. When mated with the Thermal Expansion Hole Cutter, with the Depth Stop Knurls acts as a stopper, the height at where it stops upon coming in contact with the purlins; enough so that it prevents screw over-run or over-drive, provide a perfect seal to the enlarged hole, but not deform the corrugations. BDN Fasteners polycarbonate roof fasteners are designed to create precise thermal expansion holes for fixing polycarbonate roof sheets.