Diner sandwiches are a classic American staple, often served with fries and a pickle. The most popular diner sandwiches include melts, BLTs, and French dips. A melt is a sandwich made with melted cheese, usually on toast or a hamburger bun. BLTs are bacon, lettuce, and tomato sandwiches, usually served on toasted bread. French dips are roast beef sandwiches served on a French roll, with a side of au jus for dipping.