A rate lock is an agreement between a borrower and a lender that secures an interest rate for a specific period, protecting the borrower from rate changes during that time. This is particularly common in mortgage lending, where interest rates can fluctuate daily. A typical rate lock period can last from 30 to 60 days, depending on the lender and loan terms. Rate locks provide borrowers with stability and assurance while completing the loan process but may involve a fee or cost if extended beyond the agreed timeframe.