Air blocking panel assemblies for component racks

A computer system, comprising:

• a cabinet that comprises a component rack and that includes one or more horizontal rack spaces configured to receive server components;
• and
• an air blocking panel assembly mountable within one of the horizontal rack spaces, wherein the air blocking panel assembly is sized and shaped to block air flow through the corresponding horizontal rack space when the corresponding horizontal rack space is empty, and
• wherein the air blocking panel assembly includes
• a frame portion including a plurality of integrally formed ribs;
• a plurality of stand-offs arranged on opposing side regions of the frame portion, wherein the stand-offs are positioned to releasably mate with corresponding apertures of the component rack;
• and
• a plurality of selectively removable tooling features arranged across a face of the frame portion, wherein the selectively removable tooling features comprise selectively removable portions of the frame portion that, when selectively removed, leave remaining knockout holes that are configured to receive retention features from an external accessory.