The present disclosure relates to a sealing element for hollow sections, including a seal carrier that extends along a longitudinal axis and has two arms each of which has an outer face and an inner face and which are connected together, as one piece, at longitudinal edges that face each other such that they form a corner angle between them seals mounted on or near a free longitudinal edge of each arm and running parallel to the free longitudinal edge, on the outer face of the associated arm, and a securing device, on at least one inner face of an arm, for detachably securing the sealing element onto a corner of a hollow section. A cover cap serves to complete the sealing elements, the cap being provided, on its outer face, with one or more sealing sections designed to connect to ends of the seals of the sealing element.