PURPOSE: To facilitate the positioning of a sensor by providing two clamping plates which clamp therebetween an end part of a movable blade while making close contact the steering surface thereof and which is removably attached to the movable blade, and a vertical detecting plate for always holding the measuring sensor body for measuring the steering surface of the blade, in a vertical posture.
CONSTITUTION: After a positional relationship between a movable blade and a jig is set with the use of a positioning plate 6, an arm pressing screw type jack 3 is fastened so as to make a clamping plate 1 and an oscillatably clamping plate 2 into contact with the steering surface of the movable blade. Next, a force is effected in an overcenter direction by a screw type clamp 4 so as to press the clamp plate 2 against the movable blade steering surface in order to make the jig into close contact therewith. If the movable blade has a dihedral angle so that the operation of the movable blade is not vertical, the posture of the measuring sensor is adjusted by manipulating an adjusting screw on a vertical detecting plate 5, and accordingly, it is held to be vertical within an angle rage of 3deg. With the use of a rubber pad and the plate 2, the contact force is increased. With the provision of the plates, the mounting time for the jig can be shortened.