Do you have experiences where you want to laugh at and with the customer? Sometimes I can't resist a little tease. I have enjoyed this one many, many times.
The customer has called because they can't get the key to come out of he lock.
You know and understand, when the screws on the back of a mortise cylinder have backed out far enough, that the plug comes out just far enough to prevent the key from coming out. When I see this I use the "pinch" technique to push in the plug while rolling my thumb and fore finger to pull out the key. The motion is almost invisible and the customer can't believe their eyes. I then push the key back in and ask the customer what is wrong as they see that I am having no trouble. They try again and I smoothly take out the key when they can't. After a couple of turns I let my customer 'off the hook' and explain what is happening while fixing it. They are always laughing with relief.
I don't push it too far. I realize that this is the same as being fooled by a skilled magician. I am baffled by the trick but happy to have been fooled.