| 52 / | HD | STATIC STRUCTURES (E.G., BUILDINGS) |
| 720.1 | DF | SHAFT (I.E., ELONGATED RIGID STRUCTURE) {15} |
| 721.1 | DF | .~ Stone-like component (e.g., concrete, etc.) {2} |
| 724.1 | DF | .~.~ Having feature resisting transverse loading (e.g., beam) {4} |
| 724.5 | ![]() | .~.~.~ Having outer layer or shell |