To actually lock your interest rate, you must confirm that you intend to lock-in your rate with your lender. You’ll then most likely have to sign a rate lock agreement. If you submit a loan application without a rate lock agreement, your interest rate is usually referred to as “floating” which could change until it is actually locked.
Rate-locks expire at the end of the rate-lock period. Rate-lock periods vary in length, but are usually 30-60 days. If your loan does not close before the rate-lock expires, your rate can change. You may be able to receive an extension on your rate-lock. You may also choose to let your rate expire and re-lock a new rate. Keep in mind that you might be charged fees for either an extension or a re-lock. There will also probably be specific rules that will apply that you need to discuss with your lender.
NOTE: Make sure you know the expiration date of your rate lock agreement and understand any fees you might have to pay to extend or re-lock the interest rate.