Which component of door construction is typically the horizontal piece at the top?

The horizontal piece at the top of a door is known as the top rail. This component is crucial in door construction as it helps to provide structural integrity and defines the aesthetic outline of the door. The top rail often connects the two vertical members, known as stiles, and can also tie in with any panels or other features within the door design.

Understanding this terminology is important for anyone involved in architectural design, as it informs discussions about door styles, materials, and construction methods. The top rail can vary in thickness and width, contributing to the overall look and function of the door.