The Vale glazing bar is designed to fit onto a structural framework such as timber and can take glazing materials of polycarbonate and glass of any thickness (as long as you have long enough screws). The bar consists of a 45mm wide rubber gasket that is first laid onto the timber and secured (normally glue, but sometimes staples). The glazing sheet is then laid onto the gasket ensuring that the centre section of gasket is left clear for the fixing (there are tram lines to indicate this). The aluminium top with the gaskets pre-applied is then placed in position and screwed down to create a joining seal, it is advisable to pre-drill the aluminium. Finally the PVC top cap is snapped over the aluminium to cover the screw heads, making them water tight and a more decorative finish to the glazing bar.