no they screw off. the slot with 2 holes in the middle is for a key that comes with it. Just fits on your keychain or whatever.
This is the guy I bought mine off of.
http://cgi.ebay.com/ebaymotors/CAST-STAINLESS-STEEL-GAS-DECK-FILLER_W0QQcmdZViewItemQQcategoryZ26448QQihZ002QQitemZ4641321637QQtcZphoto
make sure to tell him to include the key