alternative back door back stairs back way bolt-hole boundary condition catch choice clause condition covert way donnee ejection seat emergency exit escalator clause escalier derobe escape clause escape route fine print fire escape given grounds inflatable slide joker kicker life buoy life net life raft lifeboat lifeline limiting condition loophole obligation parameter prerequisite pretext provision provisions proviso requisite sally port saving clause secret exit secret passage secret staircase side door sine qua non slide small print specification stipulation string terms ultimatum underground underground railroad underground route way of escape way out whereas