PURPOSE: To facilitate operation by mounting struts arranged on both sides of a floating structure and bearing against the bottom surface of the structure on a beam-like jig provided on a runway and making the respective struts act toward the center of the floating structure.

CONSTITUTION: A runway 20 is mounted on a ship building berth 25 located and arranged on both sides of a floating structure 10, and beams 4 are arranged over both sides of the structure 10 on the runway 20. On the beams 4 are mounted a plurality of struts 5 the upper portion of which bears against the shell 16 of the bottom of the structure 10. Also a plurality of engaging holes 14 are provided in the beam 4 while carrier members 6 are attached respectively to the outside of the struts 5. A fastening member 7 is inserted between the carrier member 6 and any of said engaging holes 14 and fastened by a double nut so that working force given by the struts 5 acts on the structure 10 in the direction of the center. Also, similar working forces act on the bow and stern through rebound steel members 8.