The renovate key screen allows you to make a key to the selected room. You can then give keys to other players to allow them access to a locked room in your building.
Clicking the Make button will make a new key and place it in your backpack you can then give the key to whoever you wish to give them access to that locked room.
If you are giving out a key to a room inside your building but not the entrance room you will have to either leave the entrance room unlocked or give out a second key to access the entrance room otherwise whoever has the first key will not be able to get inside the building to move to the right room to use the key.