| 52 / | HD | STATIC STRUCTURES (E.G., BUILDINGS) |
| 633 | DF | OPENWORK; E.G., TRUSS, TRELLIS, GRILLE, SCREEN, FRAME, OR REBAR CHAIR {12} |
| 648.1 | DF | .~ Three-dimensional space-defining {9} |
| 651.01 | DF | .~.~ Vertically oriented (e.g., tower, etc.) {4} |
| 651.05 | DF | .~.~.~ For supporting hoisting or boring equipment (e.g., derrick, gantry) {1} |
| 651.06 | ![]() | .~.~.~.~ Inclined struts or ties meeting at intermediate runner |