Panduit TLBP1S-V Tool-Less Blanking Panel, 1U Square Hole, 5 Pack

Five 1U blanking panels that snap into square-hole rails with no screws and no cage nuts. Push in, done.

Every open rack unit in front of a switch is a short circuit for cold air — it comes out of the front of the cabinet and goes straight back in the intake without ever passing through anything. Blanking the gaps is the cheapest thermal work in the room, and tool-less means it actually gets done rather than deferred until someone finds the cage nut tool.