My cache is a hybrid letterbox cache containing a log book to sign and I put in some swag.There is also a stamp so that you can stamp your book if you collect stamps and book to place your own stamp and date and sign it.
The cache is a round plastic bottle placed far back in the letter box where the milkman use to leave his bottles. You dont need to look inside the place where the letters go. The owner of the letterbox knows that the cache is there and you may sit on his steps while filling in the log and stamping the stamp log book. There are also some items to swap.
My grandparents will maintain the cache in my absence but I often come to Wanganui in the holidays and I love geocaching