Metal double-sided tooth and slide fastener

A metal double-sided tooth having a coupling head, a body disposed at the rear end of the coupling head, and a pair of left and right legs extending from the rear end of the body, wherein the body has a front side and a rear side, the coupling head includes a flat plate portion, and a thickness of the flat plate portion is smaller than a thickness of the body from the front side to the rear side;

• a pair of coupling convex portions protruding from a front side and a rear side of the flat plate portion, front-side protruding portions disposed on left and right sides of the coupling convex portion on the front side of the flat plate portion and protruding to a height equal to a height of the front side of the body, rear-side protruding portions disposed on left and right sides of the coupling convex portion on the rear side of the flat plate portion and protruding to a height equal to a height of the rear side of the body, and a pair of coupling concave portions, wherein a front side coupling concave portion is surrounded by the coupling convex portion on the front side of the coupling head, the front-side protruding portions, and the body, and a rear side concave portion is surrounded by the coupling convex portion on the rear side of the coupling head, the rear-side protruding portions;
• an upper surface of the front side protruding portions and the front side of the body are on the same plane, and an upper surface of the rear side protruding portions and the rear side of the body are on the same plane;
• a front boundary between the front side coupling concave portion and the front side of the body is an inclined surface, and a rear boundary between the rear side coupling concave portion on the rear side of the coupling head and the rear side of the body is an inclined surface;
• a front concave portion is formed on the front boundary and has an inclined bottom and a rear concave portion is formed on the rear boundary and has an inclined bottom, wherein an inclination angle of the inclined bottom of the front concave portion is different than an inclination angle of the front boundary, and an inclination angle of the inclined bottom of the rear concave portion is different than an inclination angle of the rear boundary;
• and
• the front concave portion has a concave shape open to a top side of the metal double-sided tooth and the rear concave portion has a concave shape open to a rear side of the metal double-sided tooth.