Scumbumbo over at Mod The Sims has just released a “lockable doors” mod for The Sims 4, which means locking doors and gates on your lots has become reality. Click here to download.
Door locks can only be set on a sim’s home lot. They have to “own” the doors. It may be possible to enable locking doors at venues (e.g. gender-specific restrooms at the bars) at some point in the future.