Lever latch for locking a leaf, which comprises: - a support body, which is susceptible of being embedded in a shaped cavity of a leaf, and is provided with: - an elongated main extension in a longitudinal direction, - at least two opposite lateral walls (3, 4) delimiting a containment chamber open at the top; - a guide in communication at a first end with said containment chamber and provided at the other second end with an outlet opening; - an actuation lever, which is hinged to said support body within said containment chamber by means of a first pin arranged along a first transverse axis and engaged at its ends in opposite seats, made on the lateral walls (3,4) of said support body; - an elongated plate-like spring engaged at a first end with a second pin mechanically associated with said actuation lever having a second transverse axis (X') and arranged at a distal position with respect to said first transverse axis; - a locking rod, slidably engaged in the guide of said support body, and provided: - with a first free termination susceptible of being engaged in a hole of a fixed frame or of a floor and - with a second termination fixed to the second end of said elongated plate-like spring; said actuation lever being actuatable to rotate around said first pin between a first angular end stop position, in which the first free termination of said locking rod projects from the outlet opening of said guide, and a second angular end stop position, in which said locking rod is more retracted in said guide, characterized in that: the lateral walls (3, 4) of said support body are provided with a plurality of opposite seats aligned along the longitudinal direction of said support body, and susceptible of selectively receiving the ends of said first pin in order to vary the position of said actuation lever and of said locking rod along the longitudinal direction of said support body. - a support body, which is susceptible of being embedded in a shaped cavity of a leaf, and is provided with: - an elongated main extension in a longitudinal direction, - at least two opposite lateral walls (3, 4) delimiting a containment chamber open at the top; - a guide in communication at a first end with said containment chamber and provided at the other second end with an outlet opening; - an elongated main extension in a longitudinal direction, - at least two opposite lateral walls (3, 4) delimiting a containment chamber open at the top; - a guide in communication at a first end with said containment chamber and provided at the other second end with an outlet opening; - an actuation lever, which is hinged to said support body within said containment chamber by means of a first pin arranged along a first transverse axis and engaged at its ends in opposite seats, made on the lateral walls (3,4) of said support body; - an elongated plate-like spring engaged at a first end with a second pin mechanically associated with said actuation lever having a second transverse axis (X') and arranged at a distal position with respect to said first transverse axis; - a locking rod, slidably engaged in the guide of said support body, and provided: - with a first free termination susceptible of being engaged in a hole of a fixed frame or of a floor and - with a second termination fixed to the second end of said elongated plate-like spring; - with a first free termination susceptible of being engaged in a hole of a fixed frame or of a floor and - with a second termination fixed to the second end of said elongated plate-like spring;