Although Garry's Mod is listed as a full game, it has no objectives and instead gives the player a sandbox to manipulate items free of restrictions like furniture, and props – various objects that players can place in-game. Props can be selected from any installed Source engine game or from a community created collection. The Physics Gun allows objects to be picked up, adjusted, and frozen in place. The Tool Gun is a multi-purpose tool for performing tasks, such as constraining props together, creating interactive buttons, and creating controllable winches and wheels. The Tool Gun is also used to control add-ons created by the community. The game uses the Source engine's modified version of the Havok Physics Engine,[3] which allows players to build contraptions that follow the laws of physics, allowing for very real structures and experiments. Another concept in Garry's Mod is ragdoll posing. The player can instantiate a ragdoll model from a Source game and pose it using a variety of tools. This is a popular tool for making fan-made videos and machinimas.