A mounting tool includes a female member and a male member. The female member has first and second engagement grooves that arc inclined such that a distance therebetween increases toward one side, and a female-side locking projection disposed adjacent to the first engagement groove and protruding to a side of the second engagement groove. The male member has first and second rail portions that are simultaneously fittable into the first and second engagement grooves, and a male-side locking projection disposed adjacent to the first rail portion. The male-side locking projection is disposed so as to interfere with the female-side engagement protrusion while the first and second rail portions that are being fitted into the first and second engagement grooves move in an intermediate axis direction, and so as not to interfere with the female-side locking projection while the second rail portion is being slid along the second engagement groove.