LOT OF 7 EATON P24L31264AFH02 POW-R-LINE "Z-BRACKET" T268651

you are looking at the Vertical Support Rail (often called a Z-Bracket or Chassis Rail) for an Eaton Pow-R-Line 1a/2a or 3a panelboard. Specifically, a 61-inch rail is designed for a 72-inch tall enclosure. In Eaton's sizing system, the interior chassis is always shorter than the box to allow for "wire gutters" at the top and bottom. This rail is what the heavy electrical interior (the bus bars and breaker mounting plate) actually bolts into before it is slid into the wall box.