I think that is a smart decision and I wonder why you kept going back to it? A thought, if you don't mind, from someone (me) that has never done that (and is generally agnostic), just in case you ever wish to go there again: Why don't you install a knocker, such as you would at a door? If something benvolent wants to speak with you, you can open the door a bit, if something not so nice wants to enter, you keep it shut. If you can, install the knocker in a way that discourages non-benvolent things from using it.