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 (X), between a front portion and a rear portion , defining a length (L); - parallel to a lateral axis (Y), 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 (Z), 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 (Y) ; - 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 (Y); - 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 (Z), independently of one another relative to the base ; the holding piece being characterized in that : - at least one front support or at least one rear support 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 (X), between a front portion and a rear portion , defining a length (L); - parallel to a lateral axis (Y), 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 (Z), 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 (Y) ; - 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 (Y); - 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 (Z), independently of one another relative to the base ; - at least one front support or at least one rear support 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 ). <EOS>