Abstract: A door locking system for a tractor trailer cab for locking a pair of opposed doors from the inside in order to prevent them from being opened while the driver sleeps. The locking system includes a pair of links and shoe elements adapted to engage various parts of the door in a way that makes them non-removable when the links are tensioned, even when the windows are rolled partially down for ventilation. A toggle bolt assembly is provided between adjacent links to shorten the assembled links in order to pull the doors together and prevent their opening or to lengthen the assembly to release the doors. One or both of the shoes may be removable and replaceable with attachment shoes having a different shape in order to adapt the device for different door configurations.