So what would happen if a guy puts a girl in a friend zone?

Same rules apply. Girl approaches guy and tells him she likes him, guy doesn't reciprocate, guy rejects her kindly and offers possible friendship with girl, girl turns down friendship, girl walks away and never speaks to him again or go near him. Some guys whom actually really just wanted to be friends with the girl or use her for something else other than sex might feel stunned. 

Many people here would tell you the "friendzone" is a misogyny term used for entitled men who can't handle girls not accepting his advances for sex or relationship, but it really is about when it hits hard when one gender really likes the other and can't handle being around them knowing they would never be with them as a couple and only as much as friends, and especially if they have a significant other, which it hurts to see.

I continue being friends with the guy IF I can get past my attraction to him. If I can’t then we can’t be friends. If I can and we become friends there is no going back to possible relationship though. Once I’m rejected and we’re friends then we’re friends... and I don’t sleep with my friends. 

Very bad wrists and eyesight problems.....

So she would be in a friend zone.  So thank you for asking, I guess.