When you check out an item, a hidden lock file (.idlk) is placed on the file system. Once the content is checked out, you have exclusive control over its content, and others are locked out from making changes. You can check out InCopy content only; you cannot check out InDesign documents with layout information.
If you attempt to close an InDesign document containing one or more InCopy content files that are checked out to you, an alert message appears, prompting you to check in all content. If you close the document without checking in the content files, they will still be checked out to you the next time you open the InDesign document. Saving the InDesign document automatically saves every editable InCopy content file.
In the layout, select the text or graphics frames to edit and choose Edit > InCopy > Check Out.
In the Assignments panel, select the files and choose Check Out from the panel menu.
When you check out available content in InDesign, you
see the Editing icon on
the InDesign frame. In InCopy, the In Use icon
appears
on the InCopy frame and in the Assignments panel if the assignment
files are stored on a local server.