A braking device configured for use with the counterbalancing system of a garage door. The brake device includes a support bracket, a ratchet wheel, a pawl arm, and a biasing spring. The support bracket is rigidly connected to a fixed structure and has a guiding slot. The ratchet wheel is securely mounted about the overhead shaft of the counterbalancing system and has at least one notch. The pawl arm has first and second ends, the first end of the pawl arm being pivotally connected to the support bracket and the second end of the pawl arm cooperating with the guiding slot and being movable with respect to the support bracket along said guiding slot. The first and second ends of the pawl arm are further connected to flanges of a plug on either side of the overhead shaft. The biasing spring is operatively connected between the support bracket and the pawl arm so as to exert a biasing force for biasing the pawl arm towards the ratchet wheel. The pawl arm is devised so that, an element thereof is adjacent to the ratchet wheel, said element being shaped and sized to be removably insertable into at least one notch of the ratchet wheel so as to block rotation of the ratchet wheel, and thus block rotation of the overhead shaft, in the event of a failure of the counterbalancing system of the door. The brake device further includes a shear pin operatively connectable between the support bracket and the pawl arm for maintaining said pawl arm, prior to installation of the brake device onto the counterbalancing system, in an intermediate configuration between the first and second configurations. The shear pin is made of a specific material being breakable when the pawl arm is rotated with respect to the support bracket when the torsional force of the torsional spring transmitted to said pawl arm via the plus has reached a predetermined value, ensuring namely that a predetermined minimal amount of load is present is said torsional spring for counterbalancing purposes.