52 / | HD | STATIC STRUCTURES (E.G., BUILDINGS) |
578 | DF | MODULE OR PANEL HAVING DISCRETE EDGEWISE OR FACE-TO-FACE CONNECTING FEATURE {6} |
589.1 | DF | .~ Having integral key {3} |
591.1 | DF | .~.~ Key on angularly related edges or faces {3} |
591.2 | .~.~.~ Multiple, finite keys (e.g, perpendicular sawtooth) |