I'm designing a big project with a huge model and many sub assemblies and part files. The first project is done and now we are making many changes to it. I need to revise parts but need to be able to recall the orginal drawings. How can I change the part and roll a new rev and still be able to find and view the orginal part and drawing? I use .dwg and Vault. There is a column in Vault the says revision, but it's always blank. Thanks for any help.