This is cambridgeorganists.org Designed and produced by Stephen Taylor for the Cambridge & District Organists’ Association
No. 13: Teeth
Part of the voicing process for new pipe often but not always includes “nicking” or “notching” of the slot between the lower lip and the languid.
This is common on metal pipes, less so on the larger sizes, wood pipes and rarely in Eighteenth century German organs.
The nicks vary in depth and width.
They improve promptness of speech and brightness of tone.