What does it mean to "lock" a mortgage rate?

Locking a mortgage rate means that the lender guarantees a specific interest rate for a certain period of time, often while the borrower is in the process of securing their loan. This is an important feature because interest rates can fluctuate based on market conditions. By locking in a rate, borrowers can protect themselves from potential increases during the time it takes to finalize their mortgage.

While the other options mention aspects related to mortgage loans, they do not accurately describe what it means to lock in a rate. For example, keeping the loan amount constant does not relate to interest rate fluctuations, and preventing changes to loan terms or allowing for changes in payment schedules also does not pertain to the locking process. The main focus of locking a rate is on securing a specific interest rate against future changes, which is critical for budgeting and financial planning for borrowers.