Lump-sum Additional Payment
Some people just can't make extra payments. Remember that most mortgages will permit you to make additional payments to your principal at any point during repayment. Whenever you get some unexpected money, you can use this rule to make a one-time additional payment toward mortgage principal.
If, for example, you were to receive an unexpected windfall three years into your mortgage, you could apply this windfall toward your loan principal, resulting in huge savings and a shortened loan period. Unless the loan is quite large, even small amounts applied early in the loan period can produce huge benefits over the life of the loan.