I built one, once. I put it on its side, and kept it in the bedroom. Sometimes, I'd place it on the bed, poke my junk through, and ask the girlfriend to get down to it.
We did that a lot. I really liked it. Then one night, we were having our fun, she was having her way with me, and I peeked over the makeshift glory hole wall. To my surprise, she had her back to me, and she has idly doing me with a Fleshlight while watching "Letterman."
http://www.fleshlight.com/
I was going to yell at her and get all upset, but it was wetter than it's ever been, and it was tighter than its ever been, and it was warmer than its ever been, so I just shut up and went along with it. Sometimes, the illusion tops the reality. If it feels good, go with it.
She never knew that I knew. And I never peeked over the wall again. I'm just glad she kept the cat downstairs.