IBM 5280 User's Setup Procedures page 41

7. If your device has the Keylock feature, read and do the
following:
a. The keys for the Keylock feature are packaged in the customer
setup envelope. The envelope looks like this:
b. Record the identification number of the keys.
c. Insert the key and turn it to the right. If the key does not turn to
the right, try the other key.
Locked Position
User's Setup Procedures 35