Whitelist and Blacklist options are crucial parts of the Menu.
The Whitelist feature will allow other players to interact with your items, and the Blacklist feature blocks out unwanted visitors.
To Whitelist/Blacklist players, open the Whitelist/Blacklist window then click the player's name on the left side to add them to Whitelist/Blacklist.
To remove them in Whitelist/Blacklist, click the player's name on the right side to remove them.
Whitelist and Blacklist options can be found on the Menu.
Whitelist allows players to use your items on your base.
As stated on the Whitelist menu:
Players on your interaction whitelist are allowed to interact with all of your items. This includes moving structures, adjusting settings, [grabbing] items, driving vehicles, cutting wood, etc.
There are also 'trolls' who will pretend to be friendly to get you to whitelist them so they can help you, or even get a ride in your car, but then steal or displace your structures.
Whitelisted players cannot delete structures, but they can still move them.
Players do not need to be whitelisted to fill in blueprints and process wood in your sawmill.
Don't whitelist unfamiliar players if they ask you if they can help, as it yields many risks.
Also be careful for people who have many items because they may have stolen them from others.
The Blacklist option blocks out unwanted visitors; it creates an invisible barrier around your base that restrains blacklisted players 10 units away from your plots. Players you blacklist will not be able to enter your base, regardless of whether they are on foot or in a vehicle.
As stated on the Blacklist menu:
Players on your blacklist will not be allowed to approach your property. Put players on your blacklist if you wish not to be disturbed while building or if a player is harassing you.
They are also unable to bring wood, items, or logs to your base as the barrier blocks them and their items from reaching the base.
If you blacklist players while they are on your land, they will be instantly teleported to their spawn location. This is best used for keeping scammers, bullies and other players out so you can work in peace.
Note that, even in laggy servers, the blacklist wall will react to the blacklisted person's presence when they are on your base.
Please note that blacklisting someone with a vehicle inside may cause damaging vehicle glitches.
Greylisting is the act of both whitelisting and blacklisting someone. This means that they can drive your cars, pick up your axes and your wood, but they are unable to enter your base. When this is the scenario, someone could, for instance, help you chop wood but there is no risk of your items being messed with.