A sliding sash assembly for use as a door or window includes: (a) a frame defining a frame opening; (b) a pair of sashes mounted in the frame opening and slidable relative to each other along an opening axis between a closed position and an open position; and (c) at least one stop device including a housing and a pair of depressible stop members movably mounted in the housing. The stop members are spaced apart from each other along the opening axis. Each stop member is selectively movable independent of the other stop member between a retracted position in which the stop member is retracted into the housing and an advanced position in which the stop member projects from the housing for engagement with one of the sashes to restrict movement of the sashes relative to each other toward the open position.