To enable a same pipe to be used for eaves having different eaves plate projecting length by constructing an arm with a pipe structured to be reinforceable according to the eaves plate projecting length, and to make it unnecessary to prepare a plurality of kinds of pipe according to the projecting length of eaves plates.

An arm 4 supporting an eaves plate is made of a hollow metallic pipe 40 formed by aluminum extrusion process and the like. Inside the pipe 40, a cylindrical wall 41 is integrally formed in the center position and reinforcement ribs 42 located along the radial direction at equal angle positions of the periphery of the cylindrical wall 41 are integrally formed over the entire length of the pipe 40 respectively. Hollow parts a to d between the reinforcement ribs 42, 42 adjacent to each other are formed such that a rod-like metallic reinforcement material 5 can be fitted and inserted into the hollow part substantially over the whole length of the pipe 40.