In aviation, a clock position refers to a horizontal direction; it may be supplemented with the word high or low to describe the vertical direction which is pointed towards your feet. 6 o'clock high means behind and above the horizon, while 12 o'clock low means ahead and below the horizon. The 1949 movie Twelve O'Clock High takes its title from the system. In this case, the position would be ahead and above the horizon. The phrase "on your six" refers to the system, six referring to the six o'clock or following position.