A Coach Screw is a heavy duty wood screw primarily used for timber but can be used in plastic or in a nylon plug. The fixing has a square or hexagonal head and an externally threaded cylindrical shaft that tapers to a point at the tip often called a gimlet point. The metric sizes are manufactured to Din 571 and the square head version are normally imperial sizes to British Standard although we can produce metric sizes with a square head depending on quanity and diameter.