"Weaver" is a certain size rail that is skinny at the bottom, and thicker at the top. It is the standard mount for most Red dot sights and scope rings. There are also hand-grips, flashlights, lasers,...
Its really depending on the length of the rail. The Steyr Mannlicher Scout (my rifle ;P) has really short weaver railing; called Weaver Scope Mounting Rails. The only real thing you would want to put...
Unscrew the barrel, take off the hopper. Then unscrew all of the medium screws and take the shroud out and the left receiver half off. then lift up the stock out of its set rings and relive pressure...