The Picatinny rail is a bracket used on some firearms in order to provide a standardized mounting platform for telescopic sights and other accessories, such as tactical lights and laser sighting modules. The standard was first published by the Picatinny Arsenal and carries the official title MIL-STD-1913. It is also known by the NATO designation STANAG 2324.

The rail is typically placed directly on the weapon’s receiver, in the position normally occupied by the rear sights. The rail’s cross-section is shaped roughly like a wide T. Scopes are mounted on the rail either by sliding them on from one end or the other, or by means of a “rail-grabber” which is clamped to the rail by means of bolts, thumbscrews or levers.