Device for covering a surface comprising: (a) A substantially rectangular cover with two longitudinal edges opposite one another and two transverse edges opposite one another, each longitudinal edge being provided with a projecting element (12, 12d) extending along said edge, (b) a drum of radius that is mounted in rotation and is designed to roll up and unroll the cover, said drum being mounted on a longitudinal translation mechanism along rails arranged on both sides of said surface, each of which is made of a section with an opening on one of the faces thereof that is oriented away from the surface to be covered, and being provided with a locking element (6a, 6c), said translation mechanism enabling the longitudinal translational movement of the drum in a first direction to unroll and deploy the cover over the surface to be covered, and in a second direction to roll up and withdraw the cover from said surface, (c) a deflection pulley provided on each side of the surface to be covered to guide and position said projecting element (12, 12d) of each longitudinal edge of the cover opposite the opening of the corresponding rail during translational movement of the drum in the first direction to unroll the cover, (d) a continuous locking system for locking the projecting element (12, 12b) of the longitudinal edges of the cover in the opening of said rails, enabling the projecting element to be locked with the locking element (6a, 6c) of the corresponding rail, once the projecting element has been engaged in the opening and as the cover is unrolled, and the projecting element to be released by disengaging from the locking element (6a, 6c) during translational movement of the drum in the second direction and as the cover is rolled up, characterized in that the projecting element of each longitudinal edge of the cover includes a multitude of discrete elements distributed along each longitudinal edge, and in that • the discrete elements have an average length and are arranged side by side along the corresponding longitudinal edge, separated from one another by an average distance (d) that is equal to or greater than 0 and is preferably less than L, forming projecting units of average length (Lu = L + d), in which the average length and average distance (d) are measured parallel to the rails when the cover is deployed, • each discrete element has a mechanical flexural rigidity at least two times greater than the mechanical flexural rigidity of the cover, and • the average length (Lu) of the projecting units does not exceed 2 π R / N, in which N ≥ 10 is a real number. (a) A substantially rectangular cover with two longitudinal edges opposite one another and two transverse edges opposite one another, each longitudinal edge being provided with a projecting element (12, 12d) extending along said edge, (b) a drum of radius that is mounted in rotation and is designed to roll up and unroll the cover, said drum being mounted on a longitudinal translation mechanism along rails arranged on both sides of said surface, each of which is made of a section with an opening on one of the faces thereof that is oriented away from the surface to be covered, and being provided with a locking element (6a, 6c), said translation mechanism enabling the longitudinal translational movement of the drum in a first direction to unroll and deploy the cover over the surface to be covered, and in a second direction to roll up and withdraw the cover from said surface, (c) a deflection pulley provided on each side of the surface to be covered to guide and position said projecting element (12, 12d) of each longitudinal edge of the cover opposite the opening of the corresponding rail during translational movement of the drum in the first direction to unroll the cover, (d) a continuous locking system for locking the projecting element (12, 12b) of the longitudinal edges of the cover in the opening of said rails, enabling the projecting element to be locked with the locking element (6a, 6c) of the corresponding rail, once the projecting element has been engaged in the opening and as the cover is unrolled, and the projecting element to be released by disengaging from the locking element (6a, 6c) during translational movement of the drum in the second direction and as the cover is rolled up, • the discrete elements have an average length and are arranged side by side along the corresponding longitudinal edge, separated from one another by an average distance (d) that is equal to or greater than 0 and is preferably less than L, forming projecting units of average length (Lu = L + d), in which the average length and average distance (d) are measured parallel to the rails when the cover is deployed, • each discrete element has a mechanical flexural rigidity at least two times greater than the mechanical flexural rigidity of the cover, and • the average length (Lu) of the projecting units does not exceed 2 π R / N, in which N ≥ 10 is a real number.