"Hot Knives"...first time I've heard that term. Had to look it up,
and yes, there's even a wiki for it..
https://en.wikipedia.org/wiki/Spots_(cannabis)
Sounds like an early version of what today is called "dabbing".
Here's a typical dab rig:
Instead of a standard bowl, you use a quartz glass dabbing bowl
(often called a "banger"..dumb name, lol).
Using the torch, you heat the bottom/side of the bowl to the
point it is almost glowing, then using the dab tool (center) you
"dab" a small amount of BHO in the bowl. The bowl is so hot that
the oil vaporizes, and you inhale the vapors.
A gram of decent BHO at the dispensaries here runs $20-$60,
depending on strain and quality.