 Chell is sometimes provided with cubes that she can pick up and use to climb on or to hold down large buttons that open doors or activate mechanisms.Particle fields, known as "Emancipation Grills", occasionally called "Fizzlers" in the developer commentary, exist at the end of all and within some test chambers; when passed through, they will deactivate any active portals and disintegrate any object carried through.These fields also block attempts to fire portals through them.