Let's say you're building a birdhouse from a public domain woodworking plan, and you get to the part where you're going to mount the roof onto the rest of the house. And... it's 1/4" too short! How did that happen? You go back and check the plans again, and sure enough, you have measured everything just right. Well, time to call the manufacturer of the plans and give them a piece of your mind, right? Wrong... There's no one to call and complain to. Why? The plan is in the public domain, it was free, and whoever reprinted it with the measurement error on it most likely cannot be found. (And even if you could find them, it wouldn't do any good. Since you got the plan for free, it's not like you can ask for your money back!)

The point is, measure, and double-check everything before you start to build. That's solid advice even when you buy a plan that comes with a warranty. But if you're going to use public domain woodworking plans, it's even more important, because these plans have been passed down through the years, copied and re-copied, and sometimes an error will creep in here or there.

Don't panic - there are not a lot of errors everywhere you look. It's just important and prudent to understand the nature of public domain woodworking plans, and carefully measure and double-check things as you go along.

And, as mentioned above, that's the best advice for ANY woodworking plans, not just public domain ones