A fastening buckle adapted to bring a first side loser to a second side, including a cap fixed on the first side, a lever pivotally mounted about a first axis relative to the cap, a tie rod pivotally mounted on the lever about a second axis, the first axis being actuated, during tightening, by a translational movement with respect to the first side. An attachment rack is fixed on the second side; a latch is affixed to the tie rod, such that the latch, when closed, is engaged with one of the teeth of the rack. The cap includes two parallel side members in each of which an elongated opening is arranged. A slot is arranged in the lever between two legs; the first axis is defined by two rivets, each of the rivets fixing one of the legs to one of the side members by extending through the elongated opening so as to enable the translational movement of the lever with respect to the first side. A pinion equipped with a plurality of teeth is arranged at the end of each of the legs; the cap includes a support rack, and the teeth of the pinion are engaged with the teeth of the support rack so that the pivoting movement of the lever about the first axis generates a translational movement of the first axis with respect to the cap.