A snap hook includes a channel and an orifice of different height formed in an attaching end of a hook member and a latching cavity formed in a receiving end of the hook member, a pivotal gate having one end attached to the attaching end with an axle, and a latch member attached to the other end for engaging with the latching cavity of the hook member, the axle includes one or more flat surfaces for engaging into the narrower channel of the hook member and for selectively moving the latch member to engage with the latching cavity of the hook member and to lock the pivotal gate to the hook member, and for preventing the pivotal gate from being unlocked or opened inadvertently.