Abstract: A case composed of at least two shells. In a preferred embodiment, two semi-cylindrical shells are provided. The shells are coupled for relative rotation about an axis and are sized so that each shell segment nests within an adjacent shell. The shells are rotatable between a closed position, in which the shells cooperate to define an enclosed compartment, and an open position, in which said shells nest inside one another to provide access to the compartment.

Abstract: The present invention is a device and method for cleaning substantially planar surfaces such as glass-walled buildings. The device includes a boom and a guide structure pivotally connected to the boom to guide the boom in a forward and a reverse direction along the surface. Preferably, the guide structure is a plurality of skis. The guide structure is covered with mops which contact the surface. The boom is preferably moved in the forward and reverse directions along the surface by a tow line, a plurality of support lines, and a winch. The path of the boom is preferably guided by a pair of pulleys engaging a guide line anchored at the top and bottom of the surface.