Parametric arrow nock

This nock should be equal or superior to a professional nock bought from an archery shop. Features:
- Fully parametric so will fit your arrow spine and bow string perfectly
- Rounded cutout to aid arrow placement on string
- Bump to find what arrow side should point away from the riser when the arrow is nocked to the string
- Protrusions to "lock" the arrow while you aim
- Rounded nock floor to prevent string fraying
- Knobby protrusions for fastening to arrow without use of glue (protrusions can spell a user-defined message for extra fun)
- Slightly tapering pin for ease of insertion
- Hollow core for pin lightness
- Hole for ease of carrying or storage

You need to change the measurements in the .scad file and recompile to make it perfect for your particular arrows and - if you're picky - your bow string, otherwise you should be all set.