A slide-out support system for a flat floor slide-out room of a recreational vehicle has ways on both sides of telescoping inner rails which present a pair of downwardly facing ramped surfaces on which rollers roll to support the room. Propagating wave electromagnetic sensors monitor excitation sources in sound producing systems, such as machines, musical instruments, and various other structures. A hollow cylindrical shelf having means at one end to support a cosmetic and a pair of interior oppositely disposed male teeth adjacent its opposite end which interact with the threads enables the shelf to ride up and down on the threaded shaft as the knob is turned to thereby expose and retract the cosmetic supported at the upper end of the cylindrical shelf.