A coaster for heavy equipment in a commercial kitchen permits easier movement of the equipment for cleaning purposes. The document scanner includes a document bed having a document positioning surface, the document positioning surface arranged to receive a document placed thereon. 45 GHz RFID system of the backscatter type, to a baseband for further processing in the computer part of the unit and optionally communication with a superordinate system by a standard call channel or a Bluetooth channel. With this construction, the front and rear contacts can be installed in a stable manner. The knee bolster structure has upper and lower knee contact portions formed at front parts of the first and second knee bolster bracket members, so the knee bolster structure is used corresponding to position variation of knees of the driver. The porous, solid material having absorbed one or more semivolatile organic contaminants.