(under the class definition) Device wherein the opening extends on both sides of and through the line of juncture between a sidewall and a ceiling or roof or between two converging sidewalls, and wherein mating closures are provided, one for each barrier, or wherein a single closure is provided for the entire opening.
SEE OR SEARCH THIS CLASS, SUBCLASS:
40, for a concave or convex closure for a similarly shaped opening.
94, for a separate opening in each of two converging surfaces and closures interrelated for concurrent movement for each opening.
