PURPOSE: To provide a mast which is provided with two specially shaped sections extending spaced from each other and crossbars extending between these specially shaped sections and is hard to be bent and can behave in an aerodynamically excellent way by forming narrow concave sections in the inner surfaces of both specially shaped sections.

CONSTITUTION: Two specially shaped sections 1 spacedly arranged in a symmetric relation to each other have specially shaped inner surfaces 2, specially shaped outer surfaces 3, front ridges 4 and rear ridges 5, and the intermediate space between two specially shaped sections 1 is provided with crossbars 6 in a regular space relation. A front corner sections 7 is produced in each section where a crossbar 6 contacts the front ridge 4 of each of the specially shaped sections 1, and a rear corner sections 8 is correspondingly produced in each section where a crossbar 6 contacts the rear ridge 5. Since a virtual axis 9 extends from the front corner 7 to the rear corner 8 in each side of a mast, and the concave inner specially shaped face 2 of the specially shaped section 1 extends, the virtual axis 9 crosses most of the cross bars 6. The cross bars 6 thus absorb most of tension, making the whole of the mast hard to be bent.