Who makes chassis, rails, rack enclosures for AI data centers

The chassis and rails are the mechanical structure underneath everything else in this layer: sheet-metal trays hold the boards (4.03, 4.04) in place and mount into rails that let a tray slide in and out of the rack enclosure (4.14a) for service. Some rack-scale ODMs build their own cabinets in-house rather than sourcing a separate enclosure, which is notable because it signals how much of the rack's value they're capturing beyond just tray assembly. AI racks change the mechanical design problem in a few ways: liquid-cooling plumbing has to be routed through the chassis alongside cabling, and higher tray weight from liquid-cooling hardware and denser boards puts more load on the rails and enclosure frame than a conventional air-cooled server rack does. For investors, this tier is largely a mechanical-engineering and manufacturing-scale business rather than a technology one, so the interesting split is between the enclosure makers who sell a general-purpose cabinet platform across many customers and the ODMs who build cabinets in-house specifically to keep that margin themselves.