Shredder

From the Portal Wiki
Ha! There's our handiwork. I shouldn't laugh, really. They do feel pain. Of a sort. It's all simulated, you know. But really enough for them I suppose."
Wheatley

The Shredder (reffered to as the "spinny-blade-wall" by Wheatley) is a large pair of spinning blades used to shred Aperture Science equipment, and potentially the player. It is first seen in The Escape, where the blades destroy turrets the systems seems to be defective. Wheatley tries to use a pair to kill Chell in The Part Where He Kills You after she maneuvers past his turrets. The player must move to the left or the right to avoid them. It also appears in several Co-op course 4 chambers as a hazard.

A Shredder