respect to the bar means as the pin is moved from one terminal position in the oblong slot to the opposite one having reached such a position positive articulation and linkage is established and it is that particular point whose position with regard to a dead center position is critical in the aforedescribed operation this feature permits in turn locking of the folded up and upright locking member in the particular position namely through particular engagement with the actuator flap the release from this locking position is attained while the idle stroke is performed i e while the connecting pin between actuator flap and bar means traverses the oblong slot while the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention it is believed that the invention the objects and features of the invention and further objects features and advantages thereof will be better understood from the following description taken in connection with the accompanying drawings in which fig1 is a side view of a locking dog with locked and folded up locking element fig2 shows the same locking dog with a folded up locking element but in an unlocked i e released disposition fig3 illustrates the same locking dog shown in fig1 and 2 with folded down locking element to permit rollover by cargo but without locking the element in the folded down position and fig4 illustrates a folded down locking element of the.