Most locks require a specific property and a real loan file, so locking usually starts once you're under contract, with two exceptions worth knowing. - Lock-and-shop programs. Some lenders offer a longer window, often around 60 days, that lets you lock while you're still house hunting and close once you're in contract. The pricing is worse than a standard lock because the lender carries the risk of rates moving while you shop, so it generally only pays off in a sharply rising-rate environment. Nobody can promise which way rates head, and in a flat or falling market you're buying insurance you may not need. - A true pre-contract lock. In specific cases where the lender has full loan details and an actual property address to lock against, you can lock before the contract is signed. One compliance step follows: once you have an executed contract, the lender has to disclose the locked terms to you within three days. On expiration, the clock is set by the lock term you choose, and it isn't tied to the contract date. If your window runs short before closing, locks can usually be extended for a fee. The practical move is matching your lock length to a realistic closing timeline so you're neither paying for extensions nor letting a lock lapse.