plain rail

plain rail

In a double-hung window, a meeting rail having the same thickness as other members of the frame of the sash.
References in periodicals archive ?
3) Grinding repair to plain Rail,switches and crossings in carbon TMZ and manganese steel.
Each COP Kit includes COP/Continuous Optics Platform (upper receiver/rail), forward assist, port door rod and cover, barrel nut, two center inserts, three Picatinny rails, three plain rails, 18 screws and an Allen wrench.