We’ve all seen videos of office workers who built medieval weaponry only out of stuff they found at their desks and we’ve all been jealous of them. It always looks simple, but when we actually try and construct something, we’re the only victims of the miniature siege weapons. But Rubber Band Engineer might finally turn the tide for us. There are 19 different designs in the book, with color photos and clear instructions that guarantee your roommates, spouse, girlfriend, boyfriend, office mates, or random street passersby will never be free of your feudal warfare. All the materials can be found at your local hardware or arts and crafts store, if you don’t already have them in the house or your office’s supply closet. You don’t have any excuses to be bored at work anymore, though we can’t guarantee you’ll keep your job forever if you suddenly become Richard the Lionhearted Who Works in HR.