A ski binding device for fastening a boot on a ski is described. The device includes a toepiece and a heelpiece fixed to the ski and structured to selectively retain the boot. The heelpiece includes a turret and a hooking projecting appendix (“HPA”) that juts out from the turret towards the toepiece while remaining substantially parallel to a first reference axis. The turret having a lower casing which is fixed on a fastening base of the toepiece and a titlable upper casing resting hingedly connected thereto to the lower casing. The HPA protrudes from the titlable upper casing while remaining substantially parallel to the first reference axis, and the heelpiece includes a programmed-release locking means structured to lock and retain the upper casing until the titling torque transmitted to the upper casing exceeds a predetermined threshold value.