Abstract: A register assembly includes a register louver defining a generally circular air passage in which air directing vanes are mounted. The register louver has a central hub in which a shaft is rotatably mounted. A plurality of closure segments are mounted for rotation relative to each other about the shaft axis. Each of the segments is capable of closing a portion of the circular air passage in the louver. In a first position, the closure segments are serially aligned and substantially overlapping each other, leaving a substantial portion of the air passage open. As the shaft is manually rotated, tabs and cooperating stop surfaces on adjacent ones of the closure segments cooperate to serially rotate the closure segments from the first position, through a number of intermediate positions, and toward a second position wherein only the edge portions of the closure segments are overlapping and the air passage is completely blocked.