Dell PowerVault TL4000 - Manual (Page 234)

b. Push the end of a straightened paper clip into the access hole for each
magazine at the back of the library. DO NOT push the paper clip in more
than ½ inch.
While holding the paper clip, have a second person pull the
magazine out from the front of the unit.
Note: To prevent dropping the magazine, support both ends of the
magazine before it clears the front edge of the library.
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Figure 10-22. Access hole for the right magazine (facing rear of library)
10-24 Dell PowerVault TL2000 Tape Library and TL4000 Tape Library User's Guide