A snap hook with spring comprising at least: a main body having a first section, generally curved and a second section generally straight, the generally curved section comprises a hole and the generally straight section comprises a cavity; a sliding pin; wherein the hole receives an end of the sliding pin in a closing position of the snap hook with spring; and a spring acting on said sliding pin; a slide (1-a) formed in said main body which may have various geometric shapes leading to a travel or path, the path may comprise sections, the sections may be linear or rotational o curved or angular or any combination thereof, so there may be many paths; the sliding pin comprises a lever (2-a), wherein the lever runs the path of the slide and the path of the slide determines the type of linear or rotational movements or a combination thereof of the sliding pin, in such a way that the path of the slide is never limited to a single direction, wherein by moving the lever, an opening movement of the sliding pin begins either totally or partially linear, characterized in that: the end of the sliding pin is still partially housed in the hole located in the generally curved shape section of the main body keeping the snap hook closed during the first stage(s) of movement of the sliding pin; wherein during the first opening movement, the linear movement of the sliding pin is in a direction opposite to the end of the curved section of the body of the hook causing the end of the sliding pin to move outside the hole without leaving the same, the hole is located in the curved section of the body of the hook; wherein the end of the siding pin may remain partially or totally inside the hole of the curved section of the body of the hook during two or more direction changes in the opening movement of the siding pin; and wherein at the end of the linear or rotational movements or combination thereof the end of the sliding pin is got out from the hole located in the generally curved shape section of the main body enabling the snap hook with spring to open. a main body having a first section, generally curved and a second section generally straight, the generally curved section comprises a hole and the generally straight section comprises a cavity; a sliding pin; wherein the hole receives an end of the sliding pin in a closing position of the snap hook with spring; and a spring acting on said sliding pin; a slide (1-a) formed in said main body which may have various geometric shapes leading to a travel or path, the path may comprise sections, the sections may be linear or rotational o curved or angular or any combination thereof, so there may be many paths; the sliding pin comprises a lever (2-a), wherein the lever runs the path of the slide and the path of the slide determines the type of linear or rotational movements or a combination thereof of the sliding pin, in such a way that the path of the slide is never limited to a single direction, wherein by moving the lever, an opening movement of the sliding pin begins either totally or partially linear, characterized in that: the end of the sliding pin is still partially housed in the hole located in the generally curved shape section of the main body keeping the snap hook closed during the first stage(s) of movement of the sliding pin; wherein during the first opening movement, the linear movement of the sliding pin is in a direction opposite to the end of the curved section of the body of the hook causing the end of the sliding pin to move outside the hole without leaving the same, the hole is located in the curved section of the body of the hook; wherein the end of the siding pin may remain partially or totally inside the hole of the curved section of the body of the hook during two or more direction changes in the opening movement of the siding pin; and wherein at the end of the linear or rotational movements or combination thereof the end of the sliding pin is got out from the hole located in the generally curved shape section of the main body enabling the snap hook with spring to open. the end of the sliding pin is still partially housed in the hole located in the generally curved shape section of the main body keeping the snap hook closed during the first stage(s) of movement of the sliding pin; wherein during the first opening movement, the linear movement of the sliding pin is in a direction opposite to the end of the curved section of the body of the hook causing the end of the sliding pin to move outside the hole without leaving the same, the hole is located in the curved section of the body of the hook; wherein the end of the siding pin may remain partially or totally inside the hole of the curved section of the body of the hook during two or more direction changes in the opening movement of the siding pin; and wherein at the end of the linear or rotational movements or combination thereof the end of the sliding pin is got out from the hole located in the generally curved shape section of the main body enabling the snap hook with spring to open.