IBM 5280 User's Setup Manual page 42

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.
User's Setup Procedures 35