Nolder

In automotive design, a nolder is a small aerodynamic shape (a strip, wing, protrusion, lip or profile) integral to bodywork or to an aerodynamic attachment – e.g., a spoiler, diffuser or splitter – perpendicular to the direction of air flow travel[1] for the purpose of further managing and refining air flow.

The Formula One Dictionary defines a nolder as "a small upside-down L-shaped aerodynamic appendage generally positioned on the trailing edge of the rear wing to increase downforce at low speed.

"[4] The Automotive Dictionary defines it as a "very small aerodynamic appendage that's fitted to an airfoil to increase down-force without affecting drag resistance.

[1] Nolders are also used in less high-performance applications, for example forcing an airflow separation alongside a vertical rear window to minimize debris accumulation, e.g., with a small hatchback.

For airflow management and to assist in keeping the rear window free from dirt, nolders are integral to the rearmost vertical pillar of Mini Cooper models and the Fiat 500L.