how do you call a hand-sized plastic box with a slot cut out of one face disclosing a freely rotating bristle- encrusted wire mounted inside such that sliding the box over a surface rolls the bristle wire over it transferring dust and dirt from the surface to the box. The box also happens to pop into two pieces so the dirt can be easily removed later on, and then pop back into one piece.

I've been asking and getting no help dear reader.