Abstract: A reclosable mast (2) for drilling rig includes two opposed latticed structures (22), constrained at one end to the base structure (10) placed in the drilling site “P” and to each other, defining side faces (2b) of the mast (2). U-shaped structures, each include a rear bar (40), adapted to get compressed when closing the mast (2), and two side shoulders (41) parallel to each other and perpendicular to the an associated bar (40). The U-shaped structures are arranged at preset intervals between the two latticed structures (22), the rear bars defining the rear face or back (2a) of the mast (2). The mast (2) includes a diagonal members (3) located on the rear face 2a of the mast and constrained, between two superimposed U-shaped structures, the diagonal members (3) being adapted to split into at least two portions; reducing their longitudinal extension, and to allow reducing the dimension.