A clamp used to attach a flashlight to a firearm having a rail thereon. In the preferred embodiment, the clamp utilizes a sleeve configured to accept a handle of the flashlight. The sleeve has at least one tooth configured to engage the rail on the firearm. A wedge is movably secured to the sleeve such that a simultaneous action by the operator both forces the wedge up a ramp on an interior aspect of the clamp and secures the clamp by compressing the rail between a bracket (which engages both the clamp and the rail) and the tooth on the sleeve.