How to Block a Sender in Gmail

Apples were popular in the Middle Ages — not only as food. The after-dinner apple was also a toothbrush and cleaned molars and massaged gums. (Of course, it can still do that today, best followed by a glass of water.)
Gmail's filters are great — not only for sorting your mail. The proper rule can also clean your Inbox of, say, unwanted forwards. Maybe it massages the messages, too:
›› Are you getting nothing but jokes you did not ask for and amazing stories you don't read from a particular sender? Here's how to block them in Gmail and have all their mail sent right to the "Trash" folder, or at least out of the way for later review.