the enclosing frame around a door or window opening; "the casings had rotted away and had to be replaced"

    doorway     door     room access     threshold     window

    framework     frame     framing

the outermost covering of a pneumatic tire

    pneumatic tire     pneumatic tyre

    covering

the housing or outer covering of something; "the clock has a walnut case"

boot - protective casing for something that resembles a leg
gearbox / gear case - the shell (metal casing) in which a train of gears is sealed
jacket - the tough metal shell casing for certain kinds of ammunition

    grandfather clock     longcase clock

    housing