Mortgage interest rates change daily, meaning the mortgage interest rate you see when you first apply for your mortgage preapproval or approval may not be the same rate you end up with at closing. That’s why mortgage rate locks exist. Simply put, a mortgage rate lock freezes your interest rate until the loan closes and protects you from rising rates. What is a mortgage rate lock? A mortgage rate lock is a commitment from a mortgage lender guaranteeing that the interest rate on your home loan will remain ...