what to do is.get a pencil, draw a door, with this part situated with the "open end furthest from the door edge,then draw the chain with the flat round inserted in the slot..then on the post draw the keeper..into which will go the other end of the chain...now i have seen ones like this that have the chain in situe and the other end has a wedged blade,that is inserted into the keeper that is mounted on the post, and it can be locked from the outside...yes a lockable door chain from the outside...that allows you to give the impression that ..if an undesirable opens the door the chain runs,then stops..making them believe you are in