PURPOSE: To prevent adverse effects on a magnetic recording material and other parts, in stoppers using a permanent magnet, by preventing the leakage of magnetism to the rear sides of attachment materials from the caulking parts of the leg members of the stoppers.

CONSTITUTION: Bent leg pieces 5a and 6a of a female tool A and a male tool B of an engaging tool are inserted into attachment materials 9 and 10. The female tool A and the male tool B are attached by coupling washers 7 and 8. The attachment materials 9 and 10 are pushed up with caulking parts 2a" and 3a" of thin-diameter rod parts 2a' and 3a' of ferromagnetic projections 2a and 3a. The parts of the attachment materials 9 and 10 are housed in recess parts 7a and 8a of the washers 7 and 8, respectively. Since the caluking parts 2a" and 3a" are covered with the washers 7 and 8, leaking of magnetism to the rear sides of the attachment materials 9 and 10 from a permanent magnet 1 is prevented. Thus the adverse effect due to the magnetism is not imparted on the rear side of the attachment materials of the engaging tool.