What is Lock up ?
Lock up is (verb) 1. to close a building by locking the doors He always locks up before he goes home. She was locking up the shop when a man walked in. 2. to keep a person or thing inside a place or container by locking the door or lid Lock up the jewels in the safe or lock the jewels up in the safe. 3. to put someone in prison They locked him up for a week.
source: Easier English, Student Dictionary Upper Intermediate Level