PURPOSE: To improve the operating efficiency in repairing a thin sheet by providing the 1st and 2nd holders used for attaching and detaching a stud, to one end of a mandrel as well as providing in one body a grip to the other end.

CONSTITUTION: The 1st holder 5 is screwed in one end 2a of a mandrel 2 and the 2nd holder 9 is provided to the notch 6 of holder 5. When a chuck 11 provided to the outer circumference of holder 5 through an external thread 4 is rotated, the stud 8 is fixed between the holders 5 and 9. The stud 8 is welded to the repairing part of a thin sheet by connecting the terminal 15 of mandrel 2 to the plus side of a stud welder. After repairing the thin sheet by a grip 13 provided to the other end of mandrel 2, the welded part of stud 8 is wrenched off. In this way, the operation is simplified, and the operating efficiency in repairing is improved.