Keep track of removed items using outguides.

When a document is removed from the filing system, mark its place with an out guide.
Besides making it easier to return the document to its proper location, the out guide can hold additional information including: who has the document, when it was removed and when it is due back.
Rigid vinyl out guides feature a small pocket to hold a charge-out slip on which this information is recorded.
Manila out guides are preprinted with charge-out forms on both sides.
In addition, vinyl out guides can have a larger pocket to hold documents that are to be added to the file when it is returned.