Used to keep thieves out, or criminals inside, building locks are an essential thing in maintaining power in your location.
Building locks can only be made out of iron, and require a screwdriver to make. One building lock requires 200 grams of iron, and takes 2 days to make. You must be inside the chosen building to add a lock to it.
Please also note that this reference is in regards to a Building Lock, and not a Vehicle Lock.