The restraint room
The restraint room is a small, windowless cell at the southern end of the Green Mile, the lime-green linoleum corridor that runs the length of E Block. Unlike the six regular cells, which are arranged three on each side of the central aisle, the restraint room is located at the very bottom of the Mile, past the last occupied cell. It is a place of last resort, used when a prisoner's behavior becomes unmanageable—when they are violent, suicidal, or have simply snapped under the pressure of awaiting execution. The room is padded, with soft walls designed to prevent a prisoner from harming themselves, and it contains no furniture except for a drain in the floor. It is also used for storage when not needed for its primary purpose, holding cleaning equipment, books, and craft items, including the crayons that Eduard Delacroix later uses to color the spool for Mr. Jingles.
The Restraint Room and the Mouse
The restraint room is the site of the first appearance of the mouse that will become Mr. Jingles. The mouse scurries under the door of the restraint room during its initial visit to E Block, disappearing into the room as if it knows exactly where it is going. Paul Edgecombe and Brutus Howell later search the room for the mouse, but find no nest or hole, only a drain covered by a fine steel mesh that not even a fly could pass. The mouse's ability to enter and exit the room at will remains a mystery, adding to its uncanny nature. Percy Wetmore, who hates the mouse, chases it into the restraint room on multiple occasions, vowing to kill it, but the mouse always escapes. The room becomes a kind of sanctuary for the mouse, a place where it can hide from its tormentor.
Confinement of William Wharton
William Wharton, the violent and unpredictable prisoner who calls himself Billy the Kid, is repeatedly confined in the restraint room. After he urinates on Harry Terwilliger, the guards subdue him with a firehose and strap him into a straitjacket before locking him in the restraint room. He spends two days there, raving, promising to be good, and then screaming that he is dying. The room's padded walls muffle his cries, but the guards can still hear him. The restraint room becomes a symbol of the guards' struggle to control Wharton, a man who seems to have no fear of punishment and who delights in causing chaos. The room is also where Percy Wetmore is confined on the night of the botched execution of Eduard Delacroix, after the guards strap him into a straitjacket and gag him with friction tape.
The Final Confrontation
The restraint room is the setting for the final, terrible confrontation between John Coffey and Percy Wetmore. After being released from the restraint room, Percy walks up the Green Mile, and John Coffey reaches through the bars of his cell and grabs him. John pulls Percy to his face and transfers the tumor he had taken from Melinda Moores into Percy's body. Percy immediately goes into a catatonic state, his mind destroyed. He then draws his gun and shoots William Wharton six times, killing him. The restraint room, which had been a place of confinement and punishment, becomes the site of a kind of cosmic justice, as John Coffey uses Percy as an instrument to execute the man who truly murdered the Detterick twins. The room is also where Brutus Howell later finds the colored splinters of Mr. Jingles's spool, hidden in a hole in a beam, a final, poignant reminder of the mouse and the man who loved him.

