Then the player brings them back to the small room with the switch that activates the incinerator and carefully places them inside the doors. Test Chamber 17: After the player places the companion cube on the switch closest to the incinerator, they need to go back in the level and find a few cameras.

Test Chamber 15: Once the player reaches the room with the slow moving lifts and the energy pellet, hit both buttons to reveal the ball receiver and travel there. Test Chamber 14: Get the cube, then put it on top of the victory lift. Test Chamber 13: The player needs to get both cubes into the small starting room, and then move into the main chamber and place both portals in there. Fire both portals inside the room, and let the door close. Test Chamber 11: After getting the fully-powered portal gun, the player needs to enter the room with the energy ball launcher. Test Chamber 05: Open the exit door, shoot a portal through it, then place the cubes through the orange portal. Test Chamber 04: In the beginning, lock the door with 2 cameras and the cube.