A variation of the term "shut up," meaning to stop making noise.
Person 1: Oh, I just love having the shades open! It brings in so much sunlight that way! Don't you just love it? I can't get enough of that sunlight! Oh, I tell ya, I-
Person 2: Dude, close the shades!
The act of lowering the window shades so people walking by outside can't see you masturbating.
Has become synonymous with the act of masturbating, to where simply saying you "pulled the shades" means you rubbed one out.
College Guy 1: Hey man, you wanna go get some food?
College Guy 2: I can't right now.
College Guy 1: Why the fuck not?
College Guy 2: Because I'm about to pull the shades, man!!
Steve - "Why'd Lisa dump you?"
Larry - "She said that she didn't like the stains on her sheets that I made when I was docking the spaceship last week."