A device for positioning and clamping a planar panel in a U-shaped profile beam when the profile beam is mounted with the open end of the U shape oriented upwards, wherein the panel, when placed in a vertical position, comprises a straight underside and two planar side surfaces (5,6), the device comprising a cradle suitable for being placed inside the U-shaped cavity of the profile beam, the cradle comprising: ∘ a base for receiving the underside of the panel, ∘ lateral support elements (8,9) on either side of the base for supporting the two planar side surfaces (5,6) of the panel, ∘ one or more securing elements for clamping the panel between the lateral support elements, characterised in that the device further comprises: - a planar positioning plate inserted in an opening through the base, the positioning plate comprising a circular opening, - a planar setting plate having a circular shape that fits within the circular opening of the positioning plate, configured such that the only possible movement of the setting plate relative to the opening is a rotation about its central axis, wherein the setting plate is provided with an eccentrically placed pivot axle that is rotatable about its central axis with respect to the base of the cradle, wherein the positioning plate is wider than the width of the base, so that the rotation of the pivot axle about its central axis actuates a relative movement of the base with respect to the positioning plate when the latter is held in a stationary position, thereby enabling to set the angular position of a panel held by the device. ∘ a base for receiving the underside of the panel, ∘ lateral support elements (8,9) on either side of the base for supporting the two planar side surfaces (5,6) of the panel, ∘ one or more securing elements for clamping the panel between the lateral support elements, characterised in that the device further comprises: - a planar positioning plate inserted in an opening through the base, the positioning plate comprising a circular opening, - a planar setting plate having a circular shape that fits within the circular opening of the positioning plate, configured such that the only possible movement of the setting plate relative to the opening is a rotation about its central axis, wherein the setting plate is provided with an eccentrically placed pivot axle that is rotatable about its central axis with respect to the base of the cradle, - a planar positioning plate inserted in an opening through the base, the positioning plate comprising a circular opening, - a planar setting plate having a circular shape that fits within the circular opening of the positioning plate, configured such that the only possible movement of the setting plate relative to the opening is a rotation about its central axis, wherein the setting plate is provided with an eccentrically placed pivot axle that is rotatable about its central axis with respect to the base of the cradle, wherein the positioning plate is wider than the width of the base, so that the rotation of the pivot axle about its central axis actuates a relative movement of the base with respect to the positioning plate when the latter is held in a stationary position, thereby enabling to set the angular position of a panel held by the device.