Abstract: An assembly comprising a board 1 and a mechanism 17 for clamping a marginal portion of the board adjacent an edge between two opposed substantially flat parallel walls 7a. The mechanism 17 is mounted on a major surface 19 of the board 1 and includes a spring strip 21 extending longitudinally along the mechanism, and having corrugations transverse to its length. An elongate cam 27 extends along the length of the strip 21, overlying the strip, and being supported for rotation about its longitudinal axis. Rotation of the cam 27 causes expansion of the mechanism 17 in a direction normal to the surface 19, limitation of the expansion by the walls 7a leading to compression of the corrugations in the strip 21.