Portal 2 Chapter 4 Test Chamber 20

This is the twenty-ninth level of the game, and is the first level to be set within a fully-repaired and functional Aperture Science Test Chamber. This level requires the player to combine precise Portal-placement and multiple Thermal Discouragement Beams in order to proceed.

Hazards

 * Thermal Discouragement Beam

Walkthrough
It is also possible to complete this chamber without placing any portals if you position the cubes correctly and use a cube and quickly move the cube from side to side. If you do it correctly, holding down the strafe right movement key (default D) the door will open for a split second, letting you slip inside. This is a more difficult solution to the puzzle so the basic solution is recommended.