If you are cooking any animal with a spine then a back brace is recommended. This goes through the back of the animal around the spine and holds the carcass to the skewer. This eliminates the animal bowing while cooking.
Chicken prongs/forks are suitable for affixing chickens, rolls of meat or pretty much any meat other than whole animals to a skewer. This double prong is suitable to use in between 2 other chicken prongs and allows 2 pieces of meat to be secured.