They obstruct span-wise airflow along the wing, and are widely used specifically in early swept-wing designs.

[1] Raised in Cottbus, Germany, Liebe attended the University of Danzig, receiving his degree in aircraft engineering in 1936.

After university he joined the Deutsche Versuchsanstalt für Luftfahrt (DVL, German Research Institute for Aviation) and concentrated on the problem of preventing stall.

These trials led to a patent being granted in 1938: “Device to avoid the spread of flow disturbances”.

Somehow he ended up in Belgrade, Yugoslavia and put in charge of the development of a high performance glider aircraft.