upside down pineapple
The pineapple represents hospitality and welcoming. A pineapple is placed on a porch or mail box by swingers to signify that a swinger party is going on. A pineapple is turned upside down when a person is in search of a swinger party. Originally it was turned up side down in the individuals shopping cart. But pineapple popularity has made it accepts on clothes and other items. Swingers use this symbol to identify each other in public.
My neighbor left an upside down pineapple on my porch last night. I think he wants to swing.