I don't know if I can explain this right (I'm a French Canadian.. with an English name.. LOL).
I was once sitting at a local game, a Junior A game, about 20 years ago. I sat near the player's bench, on the side.
I've put this picture here. This is a curved (bended) glass corner, but where I was, the corner of the glass was 2 piece (like an L or a V). 90 degrees angle between the 2 pieces of glass. Anyway, there was a small crack between the 2 pieces, where the puck could pass if it was in a vertical position. I didn't mind too much after I felt "secure" about it..... until later on, the puck went through that crack and hit the row behind me. Some other kid grabbed it, but I was about 11 and I thought maybe I should have kept the puck. lol - I was "soft" back then... so I never bothered with anything, to retrieve the puck etc. (I wonder if McGuire kept that puck... he must have put it back into play).