It depends on how you are using the words. If you say, "He sold the books door to door" you mean he sold them ffrom door to door. He is then a door-to-door salesman. The hyphens are put in because...
Open the wall and build a pocket. Try an encyclopedia!!!!!
When it is a jar (ajar).When it's ajar.
here is a link to someones answer http://home.dmv.com/~warnerwerks/DJ5build.html