黑仔 is when your special wins by 5L and you walk up to the tote window then you find out it is a nil pay because you filled in R4 no3 instead of R3 no4. Or this is even worse:
Your win special copped some interference at the 50m and that roughie beat you to the 3rd place. Ok you lose on the WIN bet but get the boxed quinella ( of 2 outsiders!). Then the Enquiry sign pops up and the 4th horse protests against the winner.......Needless to say, the protest is upheld/ overruled and your WIN special is now promoted to 2nd and the bastard who knocked you off any chance is regulated to 4th ( justice!!) BUT ....you still lose heaps on the WIN bets and you also lose your only hope of breaking even with that quinella.
Its a true story because both of above happened to me during Xmas.