Abstract: A method of fabricating the lines of a taut-line platform and of prepositioning them prior to final fixing by making use of a ballastable spacer frame associated with shuttles for guiding the lines as they are constructed including preparing a floating spacer frame that is submersible by ballasting, preparing a number of shuttles of a horizontal size approximate to the group of openings through the frame to receive the same with the shuttles having releasable upper and lower mechanisms for fixing to the frame in the floating platform respectively and suspended from a second winch, being guided against rotation and having horizontal plain thrusters. After exact orientation of a platform frame assembly relative to a base, the lowering of the frame shuttle assembly is effected by ballasting the platform under guidance and shuttle thruster operation with stowing of the frame on the base occurring under conditions in which the ends of lines are permitted to heave freely in the openings of the frame.