PURPOSE: To reduce a manufacturing cost and enable speedy connection and disconnection work by providing a flat insertion section provided with sawtooth-shape projections on both sides and tilting a side on a tip side of the projection in the direction in which it widens toward the outside as it approaches a rear end side.

CONSTITUTION: An insertion section 3 is pushed between engaging pieces 6 in such a condition that the lengthwise direction of a male side connecting tool 1 becomes vertical to a base 5a of a female side connecting tool 5 and the width direction of the male side connecting tool 1 becomes vertical to a tip of the engaging piece 6 as in a state A. The engaging piece 6 is bent elastically and deformed, a tip of the engaging piece 6 rides over a sawtooth-shape projections 4, and the tip of the engaging piece 6 is engaged between the projections 4. Even if force is applied to the male side connecting tool 1 in the pull-out direction in this condition, the tip of the engaging piece 6 is caught by a side 4b on the rear end side of the projection 4, and the insertion section 3 cannot be pulled out. To disconnect it, the male side connecting tool 1 is moved in parallel up to a release hole 7 as in a state B or the male side connecting tool 1 is rotated until the width direction becomes parallel with a tip of the engaging piece 6 as in a state C to pull out the insertion section 3 from between the engaging pieces 6.