U1 makes good use of the That's Nothing signal.
See umpire on right.
Ahead of the Play
Watch how the umpire parallels the runner staying just ahead of her and arrives at his position in time to set before the play.
As R1 steals second, U1 moves down the line toward home plate to take a look at the tag at second. If U3 were blocked, he or she could possibly get help from U1.