My “concise” imperative really wanted to call this a bulletproof messenger bag, but I’m quite confident Instructables user Culturespy, author of this interesting (albeit, to my mind, slightly paranoid) tutorial, would be quick to point out that there’s no such thing as “bulletproof.” Writing a free public tutorial about how to build a piece of potentially lifesaving equipment is a touchy prospect, and, although I’m not an expert, it seems like he’s done a pretty good job of presenting the information responsibly.