a leg mating system for aligning a pre - constructed deck portion with a previously situated base portion of an offshore platform . the deck portion is supported upon a barge and brought into position above the base . a plurality of stabbing pins are hydraulically extended from the legs of the deck portion and are received in capture members in the legs of the base portion . a first spring having a first spring rate and a second spring having a second spring rate higher than the first , are operative in that order to resiliently oppose reduction of the separation between the deck and base portions with a spring rate which increases as the separation decreases . the capture members are capable of accommodating axial misalignment between the legs of the deck and base portions of up to five degrees .