The 3-piece, adjustable Guard Rail Bracket (Model Number SA-28212) consists of an upper and lower bracket and upright that fits all standard, horizontal guard rails. It must be used with our Median Barrier Sign Stand with Springs (Model M4818®). The upper and lower brackets attach to front of guard rail by hooking upper bracket and lower bracket to top and bottom of guard rail. Brackets are secured in place by turning handle to tighten. The Median Barrier Sign Stand attaches to top of the upright on the bracket and accommodates a 36" or 48" roll-up or rigid sign. It comes with two Universal Rigid Sign Brackets (for signs up to 3/4" thick), a set of Universal Roll-Up Sign Brackets and one Flag Holder Bracket (holds up to 3 wooden dowel flags -- flags sold separately).