The present invention is a reversible single-piece flex holder for retaining a flexible sign face to a sign frame. The flex holder has a latch block and a latch blade movable toward the latch block about a hinge, for clamping the margin of a sign face. A pair of pivot lips are provided on the outside of the flex holder for engagement into a slot in a sign frame. These pivot lips are symmetrical to each other relative to a clamping axis of the flex holder, such that the flex holder is interchangeably mountable to the margin of a flexible sign face. The flex holder also has a stopper lip extending from the latch block and a stopper bulge on the latch blade. The lip and the bulge interfere with each other when the latch blade is reopened to a certain extent to prevent over-stressing the hinge.