What do you call an unobstructed open edge of a fixture?

The correct terminology for an unobstructed open edge of a fixture is referred to as the "Rim." In plumbing and fixtures, the rim serves an important purpose as it allows water to flow from the fixture and typically acts as an overflow mechanism in sinks and bathtubs. Understanding this term is essential, as it relates to the design and functionality of various plumbing fixtures where proper drainage and water control are critical.

Other terms like faucet, edge, and surface do not specifically designate the open edge of a fixture in plumbing terminology. A faucet refers to a device for controlling the flow of liquid, an edge is a more general term that lacks the specific context of plumbing, and a surface typically describes the outermost layer or boundary of an object rather than an open edge. Recognizing the significance of the rim helps in comprehending the proper installation and maintenance of plumbing fixtures in accordance with code regulations.