Consider the following scene from Batman Begins, where Bruce Wayne, preparing for his new life as the Dark Knight, sharpens his bat-shaped throwing blades on an ordinary bench grinder as might be found in workshops and indeed, suburban garages around the world. Unlike much of what makes Bruce Wayne Batman—his bat-vehicles, his supercomputers, his Tibetan ninja training—this is low-tech blue-collar stuff, accessible to the home DIYer and therefore dangerous to the home DIYer, if the movie's depiction of grinder use should be unsafe. And it is.

Bruce Wayne attempts a DIY project