Abstract: A linkage for rotatably joining two members of a structure together including a rod member (1); a sleeve (8) slideable over a bifurcated, cylindrical end portion of the rod member; a link member (3) pivoted within the ends of the said end portion and having two parallel sides profiled to provide a sliding fit within the sleeve, an angled side portion (16) against which the end of the sleeve is urged when the linkage is in a partly open position and a rounded, profiled end portion to provide clearance of the sleeve when the linkage is opening; pin and guide elements (12,14) for limiting the sliding movement of the sleeve on the end portion; and a coil spring (10) located around the end portion and between one end of the sleeve and a step on the rod member to provide a torque for opening the linkage when released from the closed position.