Fascia joint covers are used to hide the 10mm expansion gap that should be left between two boards.To enable the system to expand and contract correctly in a different range of temperatures, one side of any joint or corner on any PVC fascia installation should be glued to the board and the other side should be sealed with low modulus silicon, which allows movement within the joint. Joints can be cut to size with a standard hacksaw or fine toothed saw.