In Monsters, Inc., what does Sulley use to repair Boo’s broken bedroom door?

Sulley uses a piece of wood to repair Boo’s broken bedroom door in Monsters, Inc.

At the end of the film, Sulley has recovered fragments of Boo’s door after it was destroyed during the escape from the factory. He keeps the pieces and later finds the final fragment, which includes the distinctive doorknob. With Mike’s help, Sulley reconstructs the door so he can visit Boo again.

The repaired door is one of the film’s emotional closing images. It shows that Sulley’s relationship with Boo has changed him, even though monster society originally treats human children as dangerous. The repair also gives the story a physical way to reconnect the two characters after the factory’s rules separate them.

The detail is sometimes described loosely as Sulley rebuilding the door from scraps. The key repair material shown in the story is wood, while the doorknob is the recognizable surviving piece that helps identify Boo’s door.