A vertical restraint and guide rail assembly includes a number of features which individually, or collectively, may be implemented to enhance performance. One such feature is a vertical restraint head whose forwardmost point is laterally offset from a longitudinal axis A that passes through the pivot point. A second feature is a vertical restraint head having radiused bottom surface, the lowest point of the bottom surface being aligned with the longitudinal axis A even though the forwardmost point of the vertical restraint head is laterally offset from this axis. Another feature is a pair of stops formed on the housing in which the shaft of the vertical restraint member is rotatably mounted. The stops limit rotation of the vertical restraint member to thereby reduce fatigue or hysteresis of the spring mechanism that provides a resisting force when the vertical restraint member has been deflected in either rotational direction. Yet another feature is a pair of spaced apart spring actuation bosses formed on an inner side wall of a housing bore, the spring actuation bosses comprising circumferential abutment surfaces which serve as stops for opposing side edges of a leaf spring.