Advanced jumping

Hi I have made a basic jumping script and want to make it some more advanced. I want to make it so that I can jump then I'm on top on a block but at the moment I can jump on the side and just stand there as long I press SPACE. I have tried to use tags didn't work for me so I tested texture(so I can only jump on a specific texture) didn't work.

I have this basic part in my script.

void OnCollisionEnter(Collision collision){ groundjmp = true; } void OnCollisionExit(Collision collision){ groundjmp = false; }