A mortgage rate lock freezes an offered interest rate for a set period, shielding you from increases before closing. It tends to make the most sense when your closing timeline is firm, you are comfortable with the quoted rate, and market uncertainty worries you. It is usually less attractive when your closing date is far away, rates appear likely to fall, or the lock carries stiff fees. Before deciding, compare the lock length, extension rules, float-down options, and your own risk tolerance, and consult a licensed mortgage professional for advice tailored to your loan.