Rate Lock
A rate lock is the lender's commitment that the interest rate you were quoted will not change between the lock date and closing, as long as you close within the lock period and your application doesn't materially change.
Locks typically run 30, 45, or 60 days. A standard-length lock is usually free (it's priced into the rate); longer locks or extensions cost extra, commonly a fraction of a discount point per extension. If the lock expires before closing, you either pay to extend it or take whatever the market rate is that day.
Without a lock you are floating — if rates fall before closing you win, if they rise you pay more for decades. Since market rates move every week, most borrowers lock once they have a signed purchase contract and a realistic closing date. Some lenders offer a float-down option: a lock that can be re-set once if rates drop meaningfully before closing.
A lock protects the rate, not the loan itself — final approval still depends on underwriting and the appraisal.
Related terms: Discount Points, Annual Percentage Rate (APR), Underwriting.
