When you shop for a loan, the rates and points quoted to you can change at any time. Locking in a loan rate is the only way to get the lender's commitment to that rate.

Most lenders will lock in for 15 to 30 days once you have submitted an application, which means they allow you 15 to 30 days to get approved for a loan at that rate. You'll pay anywhere from a quarter of a point to a full point to lock in a rate for 15 to 30 days. Locks over 30 days cost an additional one-eighth point for each increment of 15 to 30 days. Except for very long locks (more than 90 days), lenders add the cost to points paid at closing rather than collecting it up front.