The terms of this Guaranty may not be altered, modified, amended, supplemented or terminated in any manner whatsoever unless the same shall be in writing and signed by or on behalf of the Bank. Any Person at any time required to become a Guarantor pursuant to Section 6.13 of the Credit Agreement or otherwise shall become obligated as Guarantors hereunder (each as fully as though an original signatory hereto) by executing and delivering to the Bank that certain joinder agreement in the form attached hereto as Exhibit A .