| Mark | Description |
| BTTX | Bi-level rack |
| CTTX | Auto rack. |
| DTTX | Double-stack well car. |
| ETTX | Tri-level auto rack. |
| FTTX | Equipped to carry automobile or truck frames. |
| ITTX | Saddleback flat for carrying trucks. |
| JTTX | Miscellaneous Service |
| RTTX | Tri-Level Rack |
| TTBX | Bi-Level Rack |
| TTCX | Container-only. |
| TTDX | Military Equipment |
| TTRX | Tri-Level Rack |
| TTX | 2-Hitch TOFC |
| XTTX | 4-Hitch TOFC |