From the Project Explorer you can lock/unlock Projects or Project Reports:
This can also be done from within the Project Editor:
When a project is locked it can not be edited and when a project's reports are locked no reports can be generated for the project.
Locking can be done manually but the primary functionality is to lock based on Workflow Rules.
When a project or its reports are locked you will see the lock icon next to the project in the Project Explorer:
A user must have permission to lock/unlock projects or project reports.
When you unlock a Project or unlock the reports for a Project, the following prompt will display if there are any Workflow Rules that exist that lock Projects or Reports:
You can also lock and unlock Project and Reports from within the Project Editor. Click here for details.