In a 3-umpire system, where does the plate umpire go for help on check swings with a runner on first base?

In a 3-umpire system, when the plate umpire is unsure about a check swing with a runner on first base, they go to U1 for assistance. This is crucial because U1 is positioned along the first base line and has a better vantage point to observe the batter's action on a check swing. U1 is responsible for watching the play in the field as well as keeping an eye on plays involving runners on first base.

The collaboration among umpires is essential to ensure accurate calls are made, especially in situations where the plate umpire may not have a clear view. U1’s proximity to the first base area and their focus on plays involving the runner on first make them the most reliable source for help in determining whether the swing was a full swing or a check swing.