Real-time collaborative editing systems are distributed groupware systems that allow multiple users to edit the same document at the same time from multiple sites. A specific type of collaborative editing system is the object-based collaborative graphics editing system. fiaditionally, locking has been used as the major concurrency control techniques in this type of system. This paper examines locking in a supporting role to the concurrency control technique of multi-versioning. Two types of locks are examined: object and region. Two optional and responsive locking schemes, instant locking and instant exclusive locking, are presented. Their advantages and disadvantages are discussed.