A word of caution to all. I've spent most of my life doing drafting work and that includes making blueprints. Thay are not quite as perfect as some might think. The process has a tendancy to stretch the print ever so slightly- measuring short items gives the greatest accuracy-long distances may measure long! It all depends on many things, the humidity at the time the print was made, humidity at measurement time, type of b/p machine etc. Always, whenever possible, check direct print measurements with known published dimensions to get a feel as to how accurate your print is. And believe it or not, the thickness of the drawing has an effect on the print (light passing through, etc.). May not mean much to some people but others may want to know such things. And, the drawing was made by a HUMAN! Back in the day, things weren't as accurate as we can make them nowadays on a computer/plotter. Even some printers affect accuracy!