Abstract: A method and a device for cleaning the undersurface of footwear and wheels of shopping trolleys and other transport expedients to minimize the amount of dirt and moisture brought into a building by persons entering the building. The objective of the invention is to provide a device which provides sustained high-performance cleaning, even in adverse weather conditions and with heavy use. To this end the invention uses a mat rotated as an endless loop between guide rollers within a floor opening at an entranceway or elsewhere within a building. In a section running in one direction, the mat acts at least partially as a tread surface and absorbs dirt and moisture, while in a section running back in the opposite direction, which has gathered dirt and moisture from its exposure to persons entering the building, the mat is cleaned and reconditioned by mechanical, hydraulic or pneumatic mechanisms within the floor opening.