The holes are stretched with larger and larger plugs. When you gradate to a big enough plug, it can have a hole in it and you can see to the other side, tunnels.
"The TUNNELS? Are you kidding me? I heard Poindexter went in last semester and fucking disappeared. Screw that...besides, they're having cheesesteaks in the Dining Hall tonight and I wanna get in line before that big guy from my Chem class eats 'em all."
"I''ll tunnel it if you tunnel it." "BUT WE ONLY HAVE ONE CLIP!!" "So, i'll tunnel it, pop it out after like a minute, then you tunnel it." "Every time we do this, your shit goes everywhere, and I'm the one who has to tunnel the mess!"
"Dude, i havent stopped shitting blood since I tunneled that blunt."" "Yeah, that was awesome."
2. A feeling right before doing something uncomfortable
I was in the tunnel when I fell down in front of a huge crowd.