Sold on the Mann Co. Store, keys are used to open Mann Co. Supply Crates. A crate contains just one of several possible items listed in the crate's description. Over the lifespan of Team Fortress 2, dozens of crate variants have been released. A standard key will open any standard crate, but crates from special events must be opened with the matching special key. For example, a RoboKey is required to open a RoboCrate.