A "single crust" refers to a type of pie or tart that has only one layer of pastry, typically covering the bottom and sides of the dish but leaving the top open. This style is commonly used for fruit pies, quiches, and savory tarts, allowing the filling to be visible and often garnished. In contrast to a "double crust," which has pastry on both the top and bottom, a single crust emphasizes the filling's appearance and flavor. Popular examples include apple pie and pumpkin pie, where the crust serves as a base to hold the filling while providing a crispy texture.