Holding piece for arrangement on a channel, the channel being configured to collect an overflow of water, the holding piece being configured to hold at least one cover element (4 1, 4 1c, 4 2) covering the channel, the holding piece having a base extending: - parallel to a longitudinal axis, between a front portion and a rear portion, defining a length; - parallel to a lateral axis, perpendicular to the longitudinal axis, defining a width (l); - the lateral axis and the longitudinal axis defining a main plane (P XY), according to which the base extends, the base extending parallel to a transverse axis, perpendicular to the main plane, defining a thickness (e); the holding piece with: - at the front part, a first front support and a second front support, the first front support and the second front support being spaced from each other along the lateral axis; - at the rear part, a first rear support and a second rear support, the first rear support and the second rear support being spaced from each other along the lateral axis; - the first front support, the first rear support, the second front support and the second rear support being adjustable in height, parallel to the transverse axis, independently of one another relative to the base; the holding piece being characterized in that: - at least one front support (11, 12) or at least one rear support (21, 22) is connected to the base by means of a threaded rod, so that the height adjustment of the support (h 11, h 12, h 21, h 22) is achieved by actuating the threaded rod; in such a way that: - the heights, relative to the base, of the first front support and the first rear support can be adjusted, independently of each other, to form a support for a first cover element (4 1,4 1c); - the heights, relative to the base, of the second front support and the second rear support can be adjusted independently of one another to form a support for the first cover element (4 1, 4 1c) or a second cover element (4 2). - parallel to a longitudinal axis, between a front portion and a rear portion, defining a length; - parallel to a lateral axis, perpendicular to the longitudinal axis, defining a width (l); - the lateral axis and the longitudinal axis defining a main plane (P XY), according to which the base extends, the base extending parallel to a transverse axis, perpendicular to the main plane, defining a thickness (e); - at the front part, a first front support and a second front support, the first front support and the second front support being spaced from each other along the lateral axis; - at the rear part, a first rear support and a second rear support, the first rear support and the second rear support being spaced from each other along the lateral axis; - the first front support, the first rear support, the second front support and the second rear support being adjustable in height, parallel to the transverse axis, independently of one another relative to the base; - at least one front support (11, 12) or at least one rear support (21, 22) is connected to the base by means of a threaded rod, so that the height adjustment of the support (h 11, h 12, h 21, h 22) is achieved by actuating the threaded rod; - the heights, relative to the base, of the first front support and the first rear support can be adjusted, independently of each other, to form a support for a first cover element (4 1,4 1c); - the heights, relative to the base, of the second front support and the second rear support can be adjusted independently of one another to form a support for the first cover element (4 1, 4 1c) or a second cover element (4 2).