Screws (big head / small head) The special screw (with a length of 42mm up to 212 mm) for installing windows and doors and for the other construction work without using wall plugs. The screw is suitable for the fixing of plastic widows into brick masonry. The continuous special thread prevents the window frame from being pulled against the substrate. This means that the frame is secured to the building material without tensile force or stress. The use of screws ensures permanent fixation. The screw has a special thread with a variable height from the top of the screw which ensures easy and effective installation on various substrates.