|1.||on your six|
directly behind you. from the military designation of location where 12:00 is directly in front of you, 3:00 is to your right, 9:00 is to your left, etc.
Hang on, we've got two Japanese Zeroes on our six! I'll try to shake them!
|2.||On your six|
Watching your every move, after you, hunting you down.
If you dare mess up this deal I'will be on your six.