What structure supports a rail to form a low wall or barrier in architecture?

A balustrade serves as a structural element that supports a rail, forming a low wall or barrier. It typically consists of a series of balusters, which are short columns or supports, that help to create a barrier along stairs, balconies, and terraces. This not only provides safety by preventing falls but also contributes aesthetically to the architectural design of a space. Balustrades can be made from various materials, including wood, metal, or stone, and are often intricate in design, reflecting the style of the building.

Other structures mentioned, such as a spire, façade, and entablature, serve different purposes in architecture. For instance, a spire is a pointed roof or a tapering structure at the top of a building, often seen in church architecture. A façade refers to the face or front of a building, particularly the main entrance, which is typically designed to present an attractive appearance. An entablature comprises the horizontal sections that rest upon columns and consist of the architrave, frieze, and cornice, playing a significant role in classical architectural design but not directly supporting a rail as a balustrade does.