LOL - the pie hole is the 'enter' door and the corn hole is the 'exit' door. Best way I know how to explain it.
It is necessary to have a cornhole bag for your cornhole game because that is what you need to score points. Cornhole bags are like beanbags, and that is what you use to throw into the hole at the farthest board. If you didn't have the cornhole bags, you wouldn't be able to play this game.
Piehole
Cornhole bags are what most call bean bags. They are made of duck canvas and are filled with dried corn. Cornhole bags are used mostly in lawn games where the players stand on platforms that have holes in them.
It is 6 inches in diameter located in the center of the board and 9 inches from the top of the board to the center of the hole. For cornhole board design ideas check out: http://www.cornholeace.com/cornhole-board-designs.php
To play cornhole, you need two cornhole boards, each measuring 2 feet by 4 feet with a 6-inch diameter hole centered 9 inches from the top. Additionally, you'll need eight cornhole bags, typically made of durable fabric and filled with corn kernels or plastic pellets, with four bags per team in two different colors. A measuring tape can also be useful for setting up the distance between the boards, which is usually 27 feet apart for adults.
21
more then a few
There are several different options available online in order to find out how to sew cornhole bags. One site would be for example "Cornhole-How-To". Another one is the guide at "Big Duck Canvas Warehouse" entitled "How To Make The Best Cornhole Bags".
21 Feet
how to clean cornhole bags
Twelve or 16
Things like cornhole, ladderball, and softball