| 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} |
| 649.1 | DF | .~.~ Reinforcement for settable material {2} |
| 649.2 | DF | .~.~.~ For beam, column, etc. {2} |
| 649.3 | DF | .~.~.~.~ Having perimeter-surrounding element {1} |
| 649.4 | | .~.~.~.~.~ Helical {1} |
| 649.5 | DF | .~.~.~.~.~.~> Collapsible |