Zen students are with their masters at least ten years before they presume to teach others. Nan-in1 was visited by Ten-No2 who, having passed his apprenticeship, had become a teacher. The day happened to be rainy, so Ten-No wore wooden shoes and carried an umbrella. After greeting him, Nan-In remarked, "I suppose you left your wooden shoes in the vestibule. I want to know if your umbrella is on the right or left side of the shoes."
Ten-No, confused, had no instant answer. He realized that he was unable to carry his Zen every minute. He became Nan-In's pupil, and studied six more years to accomplish his every-minute Zen.
Notes:
1. Nan-in
2. Ten-No