I guess I should be clearer still, I already have an invisible block. I can also walk through it (this was intended). That part isn't hard. I want the part of a barrier block where you can see it if you're holding one in your hand.
Can someone explain to me how barrier blocks work? I've been hunting around for a couple hours now and can't seem to figure it out. To clarify, I want a block that is invisible until I'm holding it in my hand.