A rate lock is a lender’s promise to hold a quoted interest rate for a set number of days. That is the whole idea. Everything confusing about locks comes from the conditions attached to that promise rather than from the promise itself.
What the days actually mean
A thirty-day lock costs less than a sixty-day lock because the lender is carrying less risk. If your closing date is realistically six weeks out, a thirty-day lock is not cheaper. It is a lock you will have to pay to extend.
When floating makes sense
Floating only pays when you have both time and tolerance. If a quarter-point move would change whether you can afford the payment, that is a signal to lock, not to wait.
A lock is insurance. The question is never whether rates will fall; it is what happens to your budget if they do not.
Ask for the lock agreement in writing, check the expiry date against your contract’s closing date, and confirm the extension fee before you need it.
