Knock

A knock is referring to someone who is a fiend for drugs of any kind. weed, coke, pills, meth etc... it’s like calling someone a druggie, drug-head , tweaker, fiend, or addict.

“He pawned his family’s jewelry and tv to get drugs that guy is a straight up knock”

Drug dealer may say: “I’m going to go serve one of my knocks a gram and I’ll be back in 30”