A sheet media handling system is provided for use in a sheet processor, such system incorporating a pair of pivotal rail members which adjust laterally to afford support of variously-sized sheets. The system employs both input and output support structures, the input support structure including a pair of relatively movable side walls which adjust to accommodate sheets of different size. The rail members are linked by cooperative camming engagement with an elongate linkage arm which extends between the rail members to ensure simultaneous pivot of the rail members between respective sheet-supporting and sheet-releasing positions.