Device for the rotatable support of a shaft constituted by: a clamp 2, that couples removably with an upright M of a structure; at least one engagement element 3 removably coupling with said clamp 2 from one side and from the other side shaped to support, with substantially horizontal positioning, a reel B constituted by a band, with said engagement element 3 such as to be able to rotate with respect to its relative axis as a consequence of the winding or of the unwinding of said band, from and on said reel; a stabilisation means 4, 40, 400, 404, associated to said clamp 2, provided to stabilise the operative configurations of the engagement element 3 - reel B set and to contrast the rotation of said set in both directions.