The invention relates to a device (D) for locking/unlocking to the ground (S) of a connecting plate (100) to the ground or to the rim of a basin of a roof element, the plate (100) being on the one hand connected to the rim of the roof element and on the other hand connected to the ground (S) or to the basin rim, the plate (100) being pierced with an orifice (121) coming opposite a hole (200) made in the ground, the locking/unlocking device interacting with the hole (200) made in the ground and resting on the plate (100) for the purpose of attaching the latter. This device is noteworthy in that it comprises an expandable bush (300) changing from a volume called a rest volume allowing it to be inserted into the hole (200) made in the ground to a volume called the expanded volume ensuring its adhesion to the walls (210) of the said hole (200). Applications: attaching swimming pool shelters.