This is one of those Catch-22 deals. I am going with the probabilities here that the traveler knows less than the thieves and needs to know this, while the thieves know this…so, I am enlightening more good people than assholes.
ITS Tactical is an excellent tactical-survival solutions (skills and awareness) site. He had put together an instructive and alarming video to show you the plight for the traveler! Breaching the Zipper.
Imminent Threat Solutions (ITS Tactical) provides a wide range of topics to consider in a perhaps new way. Check it out and the zipper-pen video.