Piston

A Piston in Portal

“

You really shouldn't be here. This isn't safe for you. Click to listen — GLaDOS

”

Pistons are a hazard present in Portal, though are also sometimes required to be used as more of a game mechanic to continue through the map. Pistons kill the player by squishing them. The crusher is similar to the piston.

Portal

Portal did not feature pistons until late in the game, during Chell's escape. In Portal, pistons serve primarily as a hazard, as a player who is caught between a piston and a wall will be crushed and killed. That said, there are times where Pistons are instrumental to a player's success, such as providing a bridge in Escape 1 or propelling the player through a portal in Escape 2.

Two types of pistons are present in Portal, a cylindrical piston and a rectangular piston. The rectangular pistons are only seen once and are used to elevate Chell in order to for her to create a portal on an otherwise unreachable surface.

Portal 2

Pistons do not make as many appearances Portal 2 as they did in Portal. Often their purposes are fulfilled through crushers where the pistons would be hazards and panels where the pistons assisted the player's progress. The only instance of pistons is found during the first Conversion Gel test. Their main lack of appearance is likely due to the progression of the game, as Chell does not pass through the bowels of modern Aperture to the extent of her passage in Portal, and the older Aperture Science facilities likely did not function in the same manner as modern Aperture.