I actually make and sell these, as well as rulers that are in decimal inches. They're handy for woodworkers or others that need to use multiple scales. Even we

I actually make and sell these, as well as rulers that are in decimal inches. They're handy for woodworkers or others that need to use multiple scales. Even weirder, I've made rulers that indicate pixels at the precise PPI density for MacBook pros, iPhones, etc, so that my graphic designer friend could hand sketch UI/UX elements to scale and see how they'd render.