Some UK MRO's and Airlines jack you for a Bond of between two and five years and, if you leave, there is a sliding scale of percentage repayment rates.
Some companies have a rule that any course, of more than a few days duration, is bond-able!
Normally, the company will ask you to sign a Bond Agreement as you start the course, which is a legal contract. If you don't sign - you don't do the course. Exceptions to this are normally office staff who may not use the course (in anger) or Connies - who are paying anyway.