Bart,
There is actually a very deadly tool that has been a covert weapon for years on the streets of my country and there is good reason to believe that a tool similar to this (Or tools, plural, similar to this one...) were used by Al Qaeda to perpetrate the 9-11-01 hijackings where the aircraft were used as cruise missiles.
These things have been around forever and they can be found nearly everywhere. You could tackle a guy stocking the shelves at the local supermarket or liquor store and obtain one. In fact, although some of them are sterile and have no markings, some of them carry the names of grocery stores, liquor stores and various products from Jack Daniels to pharmacy chains.
These knives, of course, are not made by Custom Knifemakers like Barry Jones and they are not produced by mainstream knife companies like Spyderco, Camillus and Benchmade. No, quite the contrary, you can purchase or simply pick these up anywhere with no muss and no fuss and without a background check and waiting period and there is a proven track record for these devices being used by real-world terrorists. Not exactly something you dreamed up to make money while attending The Riddle of Steel. No, these are real and very well known to law enforcement.
Although there are many different types of knives like these, this particular model is one of the most heinous, in that, it is so flat, it can be worn under your foot in a shoe or left totally flat and inserted into your wallet and a lot of other places that...well, due to security reasons, I don't think it is really a smart thing to discuss it here. As you know, the Internet is in the hands of bad people everywhere, just like your book will be in the hands of bad people everywhere and...well...it's just not a good idea.
By the way, did you place "acoustic guitars and socks" in your book? If you didn't, you didn't just "miss something," you really don't have a grasp of what you are writing about.
By the way, do you know what a "Plan" is? "Le Plan?" Your book would make a great "Plan" if you would be the kind recipient of the "Plan."
Anyway, here is the picture of a real terrorist weapon and not something you dreamed up to make money. It is the one to the left. Both are deadly weapons on the street but the smaller and flatter one is really
doubleplus-ungood because of it's concealability and it is sterile by nature, you know, so it can't be traced back to The House of Saud.
You small, ignominious ring of muscle, you...