Abstract: In a friction buffer stop, each side wall of the buffer structure has at its lowermost edge mutually spaced slots extending parallel to the adjacent rail, each slot being directly opposite to and of the same length as a slot in the other side wall. Pairs of transversely spaced two-part clamps detachably secure each side wall to the rails. Each clamp comprises a pair of side plates clamped on opposite sides of the rail by a clamping bolt passing through one of the mutually spaced slots. The slots engaged by the bolts of each pair of clamps are identical in length; and the slots engaged by the bolts of each pair of clamps, except the first pair of clamps, are longer than slots engaged by the bolts of an adjacent upstream pair of clamps.