Abstract: A clamping device for locking articles onto the bar of a car top carrier, wherein the clamping device has a base member, a lever arm and a pair of links. The links are pivotally attached at opposite ends thereof respectively to the base and lever arm with the pivots spaced apart from one another and arranged so as to lock in an over-center article clamp down position. An article engaging member is secured to one of the link arms and projects therefrom beyond the lever arm adjacent one end of the same and a finger operable lever lock means is pivotally attached to the lever arm at the other end thereof and engageable with the other link for locking the lever arm in an article securing position. The base member and lever arm are channel-shaped members internested one within the other in an article locking position and have aligned apertures in such position for receiving a padlock to make the unit burglar proof.