This tip is for end-users who wish to quickly toggle the "Read Mark" attribute. I use this a lot when reading my email and wish to flag a message as UNREAD without the hassle of using the pull-down menus, so I can come back to it later and have it stand out from my read documents.
The way to toggle the read marks for documents in a view is:
Highlight the document in the view and press the insert key. This will toggle the documents' read attribute.