Abstract: The disclosure herein describes a safety fence assembly for mounting to a oor of a building under construction; it comprises guard rail structures, each formed of at least an upper rail and of a pair of uprights. Hinge elements are mounted to the opposite ends of the upper rail, at least one of the hinge elements being slidably mounted to one end of the rail. Each hinge element comprises a vertically extending pivot member which is adapted to be pivotally mounted to a post and a horizontally extending support member which includes an opening therethrough to receive the pivot member of an adjacently disposed guard rail structure. In one form of the invention, both hinge elements are movable along the upper rail while, in another form, one hinge element is fixed while the other is movable.