Foldable and flippable adapter devices, apparatus, systems and methods of attaching accessories to firearm rails. Accessories can include fore grips, and lights. Adapters can include a slidable thumb switch for locking a swinging plate with side rails to a main plate, and spring loaded detents for locking the swinging plate in substantially vertical orientations. A folding rail adapter can be substituted for the existing rail system on firearms to allow the rail to be directly attached to the firearm. A flipping rail adapter can have a pivotal lever which supports a folding rail in an open position. Springably biased detent pins allow the lever to lock open. Pushing the lever back will overcome the springs so that the pins can pass out of the detents allowing the folding rail to move to a folded position.