When you open a Revit central file for editing, ProjectWise checks out the Revit document (and its related DAT files) as usual. Then Revit prompts you to create a local copy of the central file to work from. Once the local copy is created, ProjectWise automatically checks in the central file (and its related DAT files), making the central file available again for other users to create local copies from. Once you have a local copy of a central file, you do not have to check it out again — simply continue to make changes to your existing local copy and then synchronize with central whenever you want to save your changes back to the central file in ProjectWise.