A pivotal control flap carried by the top section of one ski-braking arm is connected to an identical flap carried by the other braking arm by means of a top arcuate member. Each flap has two separate bores forming swivel-bearings respectively for the top section of the corresponding arm and for the respective leg of the arcuate connecting member. The angle made by the bores with respect to each other is such that the pivotal displacement of the two flaps under the pressure of the ski boot produces a movement of relative inward withdrawal of the bottom sections of the braking arms when they are in the raised position.