PROBLEM TO BE SOLVED: To leave at a pressurized part an easily visible mark by pressure when fastening a fastened member with a specified torque, to prevent a failure in fitting due to dimensional dispersion of the fastened member, and to enable a long-term use without generating a gap and looseness due to fatigue in a fit part.;SOLUTION: A plurality of an approximately V-shaped grooves 5, 6, 5A and 6A separated at a predetermined interval from one another are provided to at least any one surface of a pair of pressure surface 2, 3 of the fastening tool such as a spanner 1 or a monkey spanner. By visually observing the marks 14, 15 by pressure left by the fastening tool on the pressurized surfaces 12, 13 of the fastened member such as a bolt 11 or a nut having the two parallel pressurized surfaces 12, 13 opposite to each other, the fastening torque of the fastened member is confirmed.;COPYRIGHT: (C)2002,JPO
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