A support foot for supporting a free standing structure on a support surface such as a rooftop includes a holding means for holding a profiled section to which other parts of said structure can be mounted. The profiled section includes at least one wall having apertures formed in it. The support foot includes a base part having a socket. The support foot furthermore includes a securing element adapted to be received in the socket and having at least one movable catch member to catch an edge of one of said apertures so as to secure the profiled section element to the support foot. The catch member is movable from a pre-assembly position, in which it can be inserted through the aperture, to a securing position, in which it engages over the edge of the aperture.