Which ingredient is included in both the sandwich on the bottom and the heel of the 1/3 Original Six Dollar Thickburger?

The correct answer is mayo, as it is a common condiment used in many sandwiches, including the 1/3 Original Six Dollar Thickburger at Carl’s Jr. Mayo is typically spread on both the bottom sandwich bun and the heel to provide moisture and enhance the overall flavor of the burger. This ingredient seamlessly complements the other toppings and the beef patty, helping to create a balanced flavor profile.

In contrast, ketchup and lettuce might be present in other configurations, but they are not used in the same way as mayo on both parts of this specific sandwich. Dill pickles, while a popular choice, do not have the widespread application across all layers of the burger as mayo does. Therefore, mayo is the ingredient that connects both the sandwich base and its heel uniformly in this particular menu item.