This is a BAD
example of nogrenades
https://i.imgur.com/AtKddVE.jpgas you can see if a player fires a rocket within the red area their rocket will be blocked!
to prevent this from happening you should map your nogrenades like this:
https://i.imgur.com/VwPD73M.pngallowing the rockets to explode up against the wall while still preventing players from cheating the jump by shooting it
if you're confused by the images ive made an example in hammer that makes it more clear
https://www.sendspace.com/file/uv4g24edit: this is still a problem if you make the nogrenades 1 unit thick just for clarification