US Patent 10551145 Modular key-slot accessory mounting system for a firearm

An accessory mounting system for use on a firearm includes an elongated opening having first and second ends and an entry aperture between the first and second ends. A fastener with a major dimension larger than the minor dimension of the elongated opening, but small than the width of the entry aperture can be inserted into the entry aperture and slid toward either of the first and second ends of the elongated opening. The fastener may be, for example, a T-nut or a screw-like fastener with a circular head. If a T-nut is used, it can be inserted into the elongated opening transverse to the elongated opening and slide to either end in the transverse orientation so it spans across the elongated opening without having to turn it.