Device for covering a surface comprising: (a) a substantially rectangular cover having two longitudinal edges opposite one another and two transverse edges opposite one another, each longitudinal edge being equipped with a projecting bead extending along said edge, (b) a drum mounted with the ability to rotate able to roll up and unroll the cover, said drum being mounted on a mechanism for longitudinal translation along rails placed one on each side of said surface and each made up of a profile section having an opening on one of its faces and facing away from the surface that is to be covered, said face comprising at least an adjacent flange situated on the side adjacent to the surface that is to be covered and partially closing said opening, said translation mechanism allowing longitudinal translation of the drum in a first direction that causes the cover to be unrolled and deployed over the surface that is to be covered and in a second direction that causes the cover to be rolled up and removed from said surface, (c) a deflection surface provided on each side of the surface that is to be covered so as to guide and position said bead of each edge of the cover to face the opening in the corresponding rail as the drum effects the translational movement in the first direction causing the cover to unroll, (d) a system for continuously locking the bead of longitudinal edges of the cover in the opening of said rails making it possible, once the bead has entered the opening, to lock it by wedging it under the adjacent flange of the corresponding rail as the cover is gradually unrolled and, as the drum effects the translational movement in the second direction, to release the bead allowing it to disengage as the cover is gradually rolled up, characterized in that the device additionally comprises a bead engagement shoe slipped into each rail downstream of the deflection surfaces in the first direction of translation, said engagement shoe comprising: (e) an upper portion, situated outside of the rails and fixed to the translation mechanism so as to move along the rails with the drum, and (f) a lower portion, inserted in the opening in the corresponding rail, comprising a lower base the geometry of which is such that the bead is guided under the adjacent flange. (a) a substantially rectangular cover having two longitudinal edges opposite one another and two transverse edges opposite one another, each longitudinal edge being equipped with a projecting bead extending along said edge, (b) a drum mounted with the ability to rotate able to roll up and unroll the cover, said drum being mounted on a mechanism for longitudinal translation along rails placed one on each side of said surface and each made up of a profile section having an opening on one of its faces and facing away from the surface that is to be covered, said face comprising at least an adjacent flange situated on the side adjacent to the surface that is to be covered and partially closing said opening, said translation mechanism allowing longitudinal translation of the drum in a first direction that causes the cover to be unrolled and deployed over the surface that is to be covered and in a second direction that causes the cover to be rolled up and removed from said surface, (c) a deflection surface provided on each side of the surface that is to be covered so as to guide and position said bead of each edge of the cover to face the opening in the corresponding rail as the drum effects the translational movement in the first direction causing the cover to unroll, (d) a system for continuously locking the bead of longitudinal edges of the cover in the opening of said rails making it possible, once the bead has entered the opening, to lock it by wedging it under the adjacent flange of the corresponding rail as the cover is gradually unrolled and, as the drum effects the translational movement in the second direction, to release the bead allowing it to disengage as the cover is gradually rolled up, (e) an upper portion, situated outside of the rails and fixed to the translation mechanism so as to move along the rails with the drum, and (f) a lower portion, inserted in the opening in the corresponding rail, comprising a lower base the geometry of which is such that the bead is guided under the adjacent flange.