(Bicycle fork) A bicycle fork is the portion of a bicycle that holds the front wheel and allows the rider to steer and balance the bicycle.
A traditional and widely accepted way of behaving or doing something that is specific to a particular society, place, or time
custom-made: made according to the specifications of an individual
a specific practice of long standing
A thing that one does habitually
accepted or habitual practice
Established practice or usage having the force of law or right
Fork profile
I think Jim modified the fork with a rotary tool to create this notch. The notch is designed to hold the rear axle of the bike, which it grips from just inside the left rear dropout (see the next picture).
This holds the bike securely and offers significantly more control than holding by the rear wheel, while allowing the pole to be shorter and lighter.
Head Tube Spacer for Alpha Q Fork
David Lee machined a spacer to fit between the headset lower cup and the bottom of the head tube. This modification corrects the geometry to improve handling and pedal clearance with the shorter Alpha Q fork.
Notice the crack in the carbon. Time for a new fork.