The official rulebook of Major League Baseball lays out all things game-related in 123 pages. Some of the rules are fairly obvious: "The objective of each team is to win by scoring more runs than the opponent." Others are more obscure: "An indentation in the end of the bat up to one inch in depth is permitted and may be no wider than two inches and no less than one inch in diameter."

The MLB rulebook also contains a number of unenforced rules that umpires don't seem to care about and of which players are...