From Project Explorer, you can lock and unlock projects and project reports.
This can also be done from within Project Editor.
Check out this article for more details.
When a project is locked, it cannot be edited, and when a project's reports are locked, no reports can be generated for that project.
Locking can be configured based on the Workflow Rules settings in the Control Panel.
When a project or its reports are locked, you will see the lock icon next to the project in Project Explorer.
When you unlock a project or its reports, a prompt will be displayed if any workflow rules exist that lock projects or reports.