A Weaver rail mount is a system to connect telescopic sight

Telescopic sight

A telescopic sight, commonly called a scope, is a sighting device that is based on an optical refracting telescope. They are equipped with some form of graphic image pattern mounted in an optically appropriate position in their optical system to give an accurate aiming point...

s and other accessories to rifles, shotguns, pistols, archery

Archery

Archery is the art, practice, or skill of propelling arrows with the use of a bow, from Latin arcus. Archery has historically been used for hunting and combat; in modern times, however, its main use is that of a recreational activity...

 bows, etc. which uses a pair of parallel rails and several slots perpendicular to these rails.

One difference between the Picatinny rail and the Weaver rail is the size of these slots, although many rail-grabber-mounted accessories can be used on either type of rail. Weaver rails have a slot width of 0.18 in (4.572 mm), but are not necessarily consistent in the spacing of slot centers. The Picatinny locking slot width is 0.206 in (5.232 mm) and the spacing of slot centers is 0.394 in (10.008 mm). Because of this, with devices that use only one locking slot, Weaver devices will fit on Picatinny rails, but Picatinny devices will not always fit on Weaver rails. The other difference is that Weaver rails are continuous, while Picatinny rails are cut by the slots (like a dotted line) to neutralize expansion caused by barrel heating.

The Weaver rail can be used to mount the following on a firearm:

• Telescopic sight
  Telescopic sight
  A telescopic sight, commonly called a scope, is a sighting device that is based on an optical refracting telescope. They are equipped with some form of graphic image pattern mounted in an optically appropriate position in their optical system to give an accurate aiming point...
  
  
• Laser sight
• Tactical light
  Tactical light
  A tactical light is a flashlight used in conjunction with a firearm to aid low light target identification, allowing the marksman to simultaneously aim and illuminate the target. Tactical lights can be handheld or mounted to the weapon with the light beam parallel to the bore...
  
  
• Reflex sight
• Vertical Forward Grip
  Vertical forward grip
  A vertical forward grip is a vertical grip that is designed to attach to a firearm for the forward hand . These aid in the maneuverability of the firearm, since the natural angle of a persons outstretched hand is more oriented to grasping objects at a vertical angle, rather than a horizontal one...
  
  

The Weaver mount is a development of William Ralph Weaver (1905 – 8 November 1975) and W.R. Weaver Co., founded in 1930 . Now known as Weaver Optics, it has been a subsidiary of Meade Instruments Corporation since 2002.

In 2008 Meade sold the Weaver Optics brand. It is currently part of ATK's Security and Sporting division in Onalaska, WI .