A common method for attaching accessories and optics to a firearm using a simple slide on and clamp method. The accessory slides over a rail and grub screws secure it in place. The current universal NATO rail is approximately 20mm at its widest point and can accept a variety of items from scopes to foregrips. Some companies have chosen to release some models of firearm with proprietry rails of different dimensions to varying degrees of success. Most rail systems are ventilated so that the rail can expand lengthways should it become hot during operation. This allows the accessories mounted on the rail to be removed easily at any point of use. It also means that the rails themselves are less likely to split or weld under heating stress.