The 3-Umpire System is the foundation from which 4-Umpire mechanics are built upon. It is crucial that you thoroughly understand 2-Umpire mechanics before you can move up to 3-Umpire mechanics, since you revert to 3-Umpire mechanics when an umpire goes out to cover a fly ball in the 4-Umpire system used by Major League Baseball, and very soon, Division 1 and 2 NCAA baseball.
There are THREE (3) situations where the PLATE UMPIRE must cover 3RD base, and one (1) situation where the PLATE UMPIRE must cover 1ST base. The 3-Umpire System must be learned thoroughly and is fundamental to your moving up to the 4-Umpire system.