A controlled-release fastening device including a toothed strap with pitched toothing, a base on which is mounted at least one main hook pivotal with respect to the base between a retaining position, in which the hook is selectively engaged between contiguous teeth of the toothing in order to hold the strap in one direction with respect to the base, and a release position, in which at least one hook is disengaged from the strap, allowing the sliding thereof relative to the base. A ratchet is mounted on the base for the gradual release of the strap by one or more teeth at a time. The ratchet including a first and a second hook mutually spaced by a non-integral multiple of the toothing pitch and capable of alternately engaging the toothing during controlled release of the strap. The first hook of the escapement ratchet mechanism coincides with the main hook and the second hook is structurally independent of the first hook, hinged on the base coaxially with the first hook and operationally connected to the first hook in order to disengage it from the toothing of the strap when the second hook is engaged therein and vice versa.