A chicken sexer is a job where, shortly after hatching, someone determines the sex of the chicken. There is no explicit knowledge on how to do that, accuracy is built up through calibrating an intuition in an apprenticeship model (you can only learn to be a chicken sexer by working repeatedly with a chicken sexer).
See also:
- Thought Leaders and Chicken Sexers makes the analogy of thought leaders that can not be proved right or wrong because knowledge is never made explicit
- This is an example of tacit knowledge like riding a bike