Abstract: The device comprises a housing encasing a pair of upper and lower hooks, for counter-rotational movements; a pair of upper and lower adjusting assemblies, vertically spaced in parallel with the pair of upper and lower hooks for positioning the latter within the housing; an actuating assembly including a double-armed pivot having a cylindrical body and a pair of radially extending arms, disposed between the pair of upper and lower hooks; and a pair of upper and lower connecting links, mounted between the double-armed pivot and the pair of upper and lower hooks. Upper and lower connecting links are different, to accommodate the cylindrical body, in all the positions of the hooks. The upper connecting link can partially wrap around, the cylindrical body. The lower connecting link can partially wrap around, the cylindrical body.