How do I unlock files?

[WALTERS, CRAIG P [AG/1000]]

We have an occasional problem where someone will lock a file and then leave
the company without unlocking it.  When this person leaves, their accounts
are deleted.

We then have a lot of difficulty unlocking the file so others can use it.  I
have tried unlocking it from an account in the cvsadmin group but this does
not unlock the file (even though it says it does).

How can I "manually" (i.e. by editing a file) unlock a file.