Becoming a chair umpire at top events takes years of officiating lower-tier matches, attending seminars, passing written tests and undergoing evaluation after evaluation--plus some luck.

FORBES: Magazine Article

With luck, after worriedly tacking to and fro between these sorts of boundary poles, plus a bunch of others, I arrive at work that works.

NEWYORKER: Wells Tower

Plus, don't tap on the back as it takes away luck.

BBC: Chinese tourists snub 'Big Stupid Clock'