A fastener for the bodies of commercial vehicles, comprising: a bar extending substantially along a straight longitudinal axis and which is pivotable on a first part of a body of a commercial vehicle according to an axis of rotation parallel to the longitudinal axis; a contact element fixable to a second part of the body, the first part and the second part being at least one movable relative to the other; at least one engaging element non-rotatably mounted on the bar in such a way that it rotates with the bar, and comprising at least one first connecting body fixed to the bar and a projecting engaging projection, the engaging projection being movable following a rotation of the bar, between a first position in which it is disengaged from the contact element and a second position in which it is engaged with the contact element; an operating lever non-rotatably mounted on the bar in such a way that it rotates with the bar, and comprising at least one second connecting body fixed to the bar and a handle, a user being able to cause a rotation of the bar and of the engaging element by acting on the operating lever; wherein: at least one of either the first connecting body or the second connecting body comprises at least one main hole extending substantially parallel to the longitudinal axis and in which the bar is inserted, and at least one first fixing through hole extending transversally to the longitudinal axis and intersecting the main hole; and the bar comprises at least one second fixing through hole extending transversally to the longitudinal axis, and axially aligned with the first fixing hole inside the main hole; and said at least one of either the first connecting body or the second connecting body being non-rotatably fixed to the bar by a permanent coupling element comprising a pin and a locking collar, the pin in turn comprising a shank comprising a first end equipped with an enlarged head and a second end to which the locking collar is rigidly connected, characterised in that the shank is inserted with interference fit both in the first fixing hole and in the second fixing hole for substantially preventing movements of the bar and said at least one of either the first connecting body or the second connecting body relative to each other. a bar extending substantially along a straight longitudinal axis and which is pivotable on a first part of a body of a commercial vehicle according to an axis of rotation parallel to the longitudinal axis; a contact element fixable to a second part of the body, the first part and the second part being at least one movable relative to the other; at least one engaging element non-rotatably mounted on the bar in such a way that it rotates with the bar, and comprising at least one first connecting body fixed to the bar and a projecting engaging projection, the engaging projection being movable following a rotation of the bar, between a first position in which it is disengaged from the contact element and a second position in which it is engaged with the contact element; an operating lever non-rotatably mounted on the bar in such a way that it rotates with the bar, and comprising at least one second connecting body fixed to the bar and a handle, a user being able to cause a rotation of the bar and of the engaging element by acting on the operating lever; wherein: at least one of either the first connecting body or the second connecting body comprises at least one main hole extending substantially parallel to the longitudinal axis and in which the bar is inserted, and at least one first fixing through hole extending transversally to the longitudinal axis and intersecting the main hole; and the bar comprises at least one second fixing through hole extending transversally to the longitudinal axis, and axially aligned with the first fixing hole inside the main hole; and said at least one of either the first connecting body or the second connecting body being non-rotatably fixed to the bar by a permanent coupling element comprising a pin and a locking collar, the pin in turn comprising a shank comprising a first end equipped with an enlarged head and a second end to which the locking collar is rigidly connected, characterised in that the shank is inserted with interference fit both in the first fixing hole and in the second fixing hole for substantially preventing movements of the bar and said at least one of either the first connecting body or the second connecting body relative to each other. at least one of either the first connecting body or the second connecting body comprises at least one main hole extending substantially parallel to the longitudinal axis and in which the bar is inserted, and at least one first fixing through hole extending transversally to the longitudinal axis and intersecting the main hole; and the bar comprises at least one second fixing through hole extending transversally to the longitudinal axis, and axially aligned with the first fixing hole inside the main hole; and said at least one of either the first connecting body or the second connecting body being non-rotatably fixed to the bar by a permanent coupling element comprising a pin and a locking collar, the pin in turn comprising a shank comprising a first end equipped with an enlarged head and a second end to which the locking collar is rigidly connected, characterised in that the shank is inserted with interference fit both in the first fixing hole and in the second fixing hole for substantially preventing movements of the bar and said at least one of either the first connecting body or the second connecting body relative to each other.