“I want to hire someone to stand outside my door and knock three times, with each knock being three years apart. At the end of the nine years I’ll reply, “Who is it?” And without delay or reply, the person on the other side of the door is to find a new job.”

“I fear one day I’ll get a knock at my front door, and I’ll answer it to find myself standing there. Then I’ll hear myself say, “Hi, I’m from the future, and I’m here to destroy you.” But that is irrational. The future me isn’t out to destroy me, because the me of my past already did a thorough job demolishing my present and possible future.”

“If I tell you I want to be a door-to-door salesman, don’t knock it.
”

“I’m a door-to-door salesman. I sell doors. If I can’t knock on yours, because you don’t have a door to knock on, I know you’ll be interested in what I’m selling.”

“A brick could be used to knock out the tooth of a giant, and then used as a replacement for that very tooth it knocked out. I’ll tell you what, you knock it out, and I’ll put the new one back in—and I’ll charge a fee for both transactions.
”

“The first door in the hall leads to youth, the second door leads to middle age, and the third door leads to the bathroom. But knock first, because I think grandpa’s in there.”

“I never got to call myself a door-to-door salesman, because, regrettably, I only ever went to one door. But one day I just might knock on another door, to be able to proudly say that I was once a door-to-door salesman.”