Fences - Hemispherical outgrowths of the receiver of a double gun that mate with the breech ends of the barrels.
The term derives from the flanges (or fences) in this position on a muzzle loading gun that were designed to protect the eyes of the shooter from sparks and escaping gasses.
Sometimes the fences of fine guns are carved into a three-dimensional form --- Deeply chiseled fences.
