While dining out with my family last week, I watched as a particular family member sat with a plate of half-eaten food in front of her for some time. After she hadn't touched it in about ten minutes, I had to ask her if she was done.
"Oh yes," she said.
"Then put your silverware together on your plate with the handles facing 5 o'clock."
No sooner had she done that than a magical server assistant appeared from out of nowhere and whisked her plate away. It took ten seconds at the most, because she finally gave him the universal sign for "I'm finished." We as servers are constantly observing to see if our patrons have finished -- it's a standard of service to remove dirty plates that the guest no longer needs. It also relates to a secret desire we have to move you along in your meal, and right on out the door.
If you are too full to finish your dinner and wonder why you've been sitting there with a plate of half-eaten food in front of you for 15 minutes, I can almost guarantee that your server thinks you're still eating it. Instead of pushing it away (rude) or putting your napkin on it (gross), just study the below pictures.
This silverware placement tells your server that you're still working on your food. Or, if you're like the restaurant in which I work, it says, "I'm still enjoying my food. I'm not 'working on it' because eating an $80 steak shouldn't feel like work.'"
This silverware placement tells your server to get this dish out of your face.
The waitstaff doesn't want to rush you, nor do we want to have to interrupt your conversation to ask if you're done. Just move that silverware to the proper position and we'll get the hint when you're ready. Give us the sign.