A screw will usually have a head on one end that contains a specially formed shape that allows it to be turned, or driven, with a tool. Common tools for driving screws include screwdrivers and wrenches. The head is usually larger than the body of the screw, which keeps the screw from being driven deeper than the length of the screw and to provide a bearing surface.
Silicon Sealant is a Specialised materials for avoiding in the water leakages from roof and cladings. It should be applied on the Screw top where our small cap in the roof area, ventilators fixing and flashings fixing