Although some people choose not to use the term “dust cover” in reference to a handgun, it refers to the forward part of the frame in a pistol. This is where a Picatinny rail accessory system could be found, if present. In a rifle, the dust cover seals the ejection port (the area that allows spent brass to exit the upper receiver after firing) from allowing contaminants such as sand, dirt or other debris into the mechanism.