This is perhaps the most important rule:
All major ingredients and condiments shall extend to all edges of the bread, so as to fill the sandwich completely. No one wants to eat a dry, empty crustal border.
No yellow mustard. You should not eat anything that color unless you are Sylvester the Cat.
I discovered recently that proscioutto does NOT work well in layers as the ham in a sandwich. Those succulent thin little slices when layered together conspire to make the sandwich tough and come off in uneven, chunky bites. I should have known better.
One of my favorite BBT scenes…
Sheldon: Well, this sandwich is an unmitigated disaster. I asked for turkey and roast beef with lettuce and swiss on whole wheat.
Raj: What did they give you?
Sheldon: Turkey and roast beef with swiss and lettuce on whole wheat. It’s the right ingredients but in the wrong order. In a proper sandwich the cheese is adjacent to the bread to create a moisture barrier against the lettuce. They might as well have dragged this thing through a car wash.
Ketchup goes on hot food; hamburgers, french fries, meat loaf, scrambled eggs, etc.
Ketchup does not go on cold food; cold cuts, cottage cheese, tunafish, potato chips, etc.
I beg to differ. Ketchup shouldn’t go anywhere.
What about “manaze & 'mater” sammiches? (Sublime.) And ketchup goes on scrambled eggs and brains.
hang on, it depends on what kind of sandwich. if you are having a Fried Egg Sandwich you have to have mayo (not miracle whip!) and, along with salt, you need nothing else.
If a peanut butter and jelly sandwich is not going to be eaten right away, spread the PB thickly on one piece of bread and then also spread the thinnest possible amount of PB on the other piece of bread before spreading the jelly, to seal the bread. Serve with Fritos, which the true PBJ aficionado will use to scrape bits of PB from the edge of the sandwich.
Also, jam is preferable to jelly, because it spreads more smoothly. Grape is preferred, but strawberry is acceptable as an alternative.
1.1: Mustard should not touch the cheese. It makes the cheese… Slimy? Yucky? Something.
1.2 Miracle Whip should not touch anything. Ever. Because it makes everything yucky.
I wholeheartedly support the position that all filling should reach every edge of the bread. Moreover, the bread should match - no divorcing slices from the partner it was born with, and for the love of God, put the faces back together to make a tidy sandwich!
Miracle Whip should not exist.
I think it’s just mayo somebody put sugar in. doesn’t make it right, of course.
This is what I was going to say. I ate PB&J almost every day in grade school, and putting peanut butter on both slices of bread was crucial to the success of the sandwich. The thought of purple, jelly-fouled bread still makes me gag a little.
- A piece of bread goes on the bottom.
- Mustard goes on the bread.
- Meat goes on the mustard
- Cheese goes on the meat
- Optional - lettuce, tomato, onion go on the cheese
- A piece of bread goes on the top
Note that only steps 1 and 6 are absolutely necessary.
I hear tell that in Norway pretty much all sandwiches are open-face.
No Ketchup. NO KETCHUP!!
Ace’s rule - Sandwich bread must be toasted. Subs should be put under a broiler to get a crispy crust.
That’s exactly why I don’t put the mustard on the bread; it soaks in a bit and messes with the distinct taste and texture of the bread.
What about a meatloaf sandwich?
That was the first thing I thought of when I saw the thread title. 
I generally agree with the No Ketchup On (cold) Sandwiches rule, but feel there should be an exception for some leftovers meats, such as on meatloaf or thinly sliced next-day barbecued tri-tip with a little provolone added. I don’t feel strongly enough to go to the mat on that, but will form a splinter sandwich schism if persecuted.