http://qkpm2ov2rjhjkhfsftskqho77uj5rewd5y44unkf6cb7tdhaxwcvh2id.onion/books/dbpf/Type%20Group%20Instance%20-%20SC4D%20Encyclopaedia.html
Typically, this involves creating a mod that has the same TGI as a Maxis object that came with the game, so that the custom mod will overwrite the default settings. An object's TGI is commonly written in full as: AAAAAAAA BBBBBBBB CCCCCCCC where "AAAAAAAA" is the Type ID, "BBBBBBBB" is the Group ID, and "CCCCCCCC" is the Instance ID. During certain modding operations, a TGI File may be generated.