Abstract: Apparatus for supporting a working platform on a roof comprises hook members for engaging the roof cap, a cable extending downwardly from the hook member and a support unit attached to the lower end of the cable and provided with a winch so that it can be moved up and down the cable. The apparatus is used in pairs or larger numbers with an elongate working platform supported on the support unit of each apparatus. The support units can roll up and down the roof on balloon tires and are provided with a chassis section lying close to and parallel to the roof so that if the support units are overloaded the balloon tires will deform and the chassis section will come into contact with the roof, thereby spreading the load and reducing the risk of damage to the roof.