A mechanical mechanism which allows a holster to firmly support and hold steady a pistol or revolver, allowing a smooth and quick release of this locking mechanism when required on the draw. This mechanical mechanism can grip the gun only on the trigger guard area, achieving a solid grip and smooth release by means of a sliding block formed around the shape of the front end of the trigger guard, which slides sideways out of the way as the gun is drawn upwards. Tension adjustment is achieved by applying more or less pressure on this sliding block as it moves up in its track, while the gun is drawn upwards. Total locking is achieved by means of a rotating lever, which locks the sliding block in place, preventing it from moving up at all, when securing the gun is required.