Question On Knifing?

My grandson has been found with burnt knives. What kind of drugs is this used for? I know he has been using pot but what else could he be using.
It could be hash.....
Here is a link to some drug info and what is used with different.
http://www.dap.ie/dap_prof/parental..._info_signs.htm
or opium....

hot knives is a disciption of two heated knives pressed together with cannibass in between which is inhaled through a bottle.