The Lock command enables you to lock one or more of your opened files. Only files opened by you in the current workspace can be locked. (See also Unlocking Files.) When a file is locked, only the user who locked the file can submit changes to that file. Other users can open locked files in their workspaces, but they can't submit changelists that include locked files.
To lock one particular file:
Selecting Lock... from the pulldown menu on the Files tab displays a form that lets you select files to lock.
If you have more than one pending changelist, you can choose to lock only the files associated with one changelist. To do this, check Lock files in changelist, select the changelist you want, and click Lock. This option locks the files in the selected changelist regardless of whether the files are in the current path. Alternatively, you can choose to restrict files to lock by path, or by selecting from a checklist. For more information, see Restricting Files Used in Commands.