expression, godan verb (-su)
lock; fasten a lock
A set phrase meaning to lock something, typically a door or gate. Often used in instructions or descriptions of securing an entrance.
外出するときは必ず錠を下ろしてください。
Please be sure to lock the door when you go out.
夜は門に錠を下ろすのを
Don't forget to lock the gate at night.