PURPOSE: To facilitate the fitting and removal of a wing by aligning openings of a wing and a vessel body each other, and forming each opening at a dimension capable of inserting a hand into a hollow inside of a vessel body.

CONSTITUTION: Each vessel body 4 is supported by a recessed deck saddle 20, and an open type conical hatch body 22 is projected upward from each deck saddle 20, and dimension and shape of the conical body 22 is determined so as to be fitted in each hatch opening 24 formed in a wing at a port side and a starboard side thereof. With this structure, the conical body 22 passed through the opening 24 automatically aligns the wing 2 with each deck saddle 20 of the vessel body, and the wings 2 form a perfect deck assembly. A clamp is engaged with a wing receptacle 28 while giving a fastening system capable of preventing projection, and the wing 2 is quickly and efficiently connected to the vessel body 4. The wing 2 is removed by removing a hatch cover 6, and removing the clamp with hand.