A selvage for a secondary wing of fire doors, of the type comprising a body provided with gears constituted by at least one laminar element (13), with which respective vertically sliding sliders (19) are associated, the sliders engaging in corresponding receptacles, one in the threshold and one in the lintel of the opening where the door is installed, the element being actuated by a panic bar for opening. A ring (25) is centrally pivoted on the bottom of the body and perimetrically with respect to the at least one laminar element (13), a rotation of the ring (25) being associated with the translational motion of the at least one element (13); the ring (25) is provided with a toothed edge (27), proximate to which a pawl-type lever (23) is pivoted, the lever being provided with a tooth (24) that can engage removably the toothed edge (27) by means of the forcing of an elastic means (28), the ring (25) being blocked when the tooth (24) is engaged in the toothed edge (27).