What form of torture is walling?

Answer 1

"Walling" is the brutal shoving of suspects against a wall.

From Serwer's account:

The Bybee memo also describes a procedure known as "walling." The detainee wears a thick collar, which the interrogator uses to throw him against a "flexible wall." This "false wall" is meant to be constructed in such a way that impact creates a loud sound. Bybee wrote, "The idea is to create a sound that will make the impact seem far worse than it is and will be far worse than any injury inflicted on an individual." In Bybee's description, the detainee's shoulder blades are meant to hit the wall, implying that the detainee's back is to the wall.

In practice though, the ICRC report indicates that Zubayda was slammed "directly against a hard concrete wall." Another detainee, Walid Bin Attash, said that he was not only slammed against the walls of his interrogation room but that he was led along the corridor by his collar and slammed against the wall as he went. Another detainee said his head was slammed against a pillar repeatedly. One of the other memos released yesterday, written in May 2005 by Steven G. Bradbury, who was then head of the OLC, indicates that "walling" could be used "20 or thirty times consecutively when the interrogator requires a more significant response to a question."