McDLT was the name of McDonald's 1980s burger box designed to keep hot and cold ingredients separate.
The McDLT was sold in packaging with two compartments: the hot side held the cooked meat and bottom bun, while the cold side held lettuce, tomato, and the top bun. Customers combined the two sides before eating. The packaging was central to the product's branding because its selling point was temperature and texture control.
McDonald's promoted the sandwich with the phrase “Keep the hot side hot and the cool side cool.” The campaign made the unusual container as memorable as the burger itself, but the package used more material than ordinary burger wrapping and the product was eventually discontinued.
The McDLT is often confused with later McDonald's sandwiches such as the Big N' Tasty or Arch Deluxe. Those products had different recipes and did not use the McDLT's signature two-sided presentation.