When a turn is at the pearly gates of your butthole.
"Dude I gotta shit so bad, it's knocking on heaven's door!"
A phrase originated from 19th century Thailand, which is often used today to describe something being weird or abnormal.
John - "Did you see that weird guy at the store?"
Mary - "Yeah, he was Knocking At The Cow's Door."
When your boomer parents still think that you can apply for jobs by physically going to a business and asking if there are any jobs available, just like they did back in the day, before the popularity of the internet or pre-2000.
Dad: why don't you get off your arse and get a job.
Son: I've been looking online for weeks and applied for everything I can, there's nothing new.
Dad: Your not looking hard enough, go out and knock on some doors. That's what I did when I was your age.
Son: Dad, nobody does that anymore, employers and job agencies do everything online now. Even the job centre posts their own stuff there.
Dad: omg kids these days, don't know how good they have it. When I was your age I walked 20 miles to work and back barefoot whilst carrying a bag of cole on my back, I got paid 2 bob a week, blah blah blah blah blah blah blah blah blah
Son: stfu dad, stop lying and get with the times.
a) the act of specifically raping a virgin teen girl in the anus
b) arriving somewhere unexpectedly, when they least expect you.
sociologist of criminal behavior, (visiting the cemetery of Marion State Prison, Illinois): Ghost Poinsalet, I hear you are famous, even among ghosts, in this cemetery. What have you been incarcerated, and executed for, 27 years ago?
ghost of Matthew Poinsalet (character from Dead Man Walking): Sir, it was for knocking at your back door, definition b), to the house of 2 virgin teen girls, then committing knocking at your back door, definition a), and then finally murdering my victims.
sociologist (under his breath): How atrocious, may we condemn all child rapists and murderers to the electric chair, Amen.