A portable security device for locking a pair of stanchions of a cargo container which employs a J bar having a hook at one of its ends for engaging one stanchion and notches on its other end which are engageable by a complementary latch on a flip plate pivotally mounted to a housing which includes an elbow providing a pocket for the other stanchion. The J bar extends through aligned opening in side walls of the housing and in front of the other stanchion to lock it in its pocket. A puck lock secured to the housing holds the flip plate latch in engagement with a notch of the J bar.