Green’s Dictionary of Slang

(NZ prison.drugs) a means of smoking marijuana by using hot knives.

1999

D. Looser ‘Boob Jargon’ in NZEJ 13 35: spot v. To take marijuana by heating two knives on a stove element, placing a drop of marijuana oil between the hot knives and inhaling the resultant smoke through a milk or Coca-Cola bottle.