(a) Adequate loan security must be provided for loans made or guaranteed by RUS. The loans are required to be secured by a first mortgage lien on most of the borrower's assets substantially in the form set forth in appendix A of this subpart. At the discretion of RUS, this model form of mortgage may be adapted to satisfy different legal requirements among the states and individual differences in lending circumstances, provided that such adaptations are consistent with the policies set forth in this subpart.(b) Some borrowers, such as certain public power districts, may not be able to provide security in the form of a first mortgage lien on their assets. In these cases RUS will consider accepting other forms of security, such as resolutions and pledges of revenues.(c) RUS may require supplemental and amending mortgages to protect its security, or in connection with additional loans.(d) RUS may also require such other security instruments (such as loan contracts, security agreements, financing statements, guarantees, and pledges) as it deems appropriate.(e) All distribution borrowers that receive a loan or loan guarantee from RUS on or after August 17, 1995 will be required to enter into a mortgage with RUS that meets the requirements of this subpart. The concurrence of any other lenders secured under the borrower's existing mortgage may be required before the borrower can enter into a new mortgage.