The Numbskull Port Door was designed to be a functional improvement upon the slick and pocket dust cover design. The NPD features two angle limiting hemispheres, at the bottom corners, giving the port door an angle that slopes away from the lower receiver, allowing for better clearance of right sided ambi controls. The additional clearance, along with the indexing ridges, in the central space, make it a easer to return to a closed postion, especially with one-handed operation.