Albus Dumbledore didn't seem to realize that he had just arrived in a street where everything from his name to his boots was unwelcome. He was busy rummaging in his cloak, looking for something. But he did seem to realize he was being watched, because he looked up suddenly at the cat, which was still staring at him from the other end of the street. For some reason, the sight of the cat seemed to amuse him.He found what he was looking for in his inside pocket.It seemed to be a silver cigarette lighter. He flicked it open, held it up in the air, and clicked it. The nearest street lamp went out with a little pop. He clicked it again -- the next lamp flickered into darkness. Twelve times he clicked the Put-Outer, until the only lights left on the whole street were two tiny pinpricks in the distance, which were the eyes of the cat watching him.

"'To Ronald Bilius Weasley, I leave my Deluminator, in the hope that he will remember me when he uses it'… "

Ron was given a Deluminator in Dumbledore's will. The trio used it when they were attacked by Death Eaters Antonin Dolohov and Thorfinn Rowle at Tottenham Court Road. Ron put the lights out while Hermione wiped the Death Eaters' memories, and he and Harry cleaned up the cafe. They used it again in the dungeon of Malfoy Manor as part of their escape.

Most importantly, Ron used the Deluminator to find Harry and Hermione after temporarily abandoning them in the winter. He instantly regretted his decision to leave, which was influenced by the negative energy within Salazar Slytherin's Locket, but was unable to find them until the sound of Hermione saying his name came from the Deluminator, which began to emit light which led him back to his friends. Ron saved Harry's life and destroyed the locket Horcrux. While Ron was glum about Dumbledore's apparent prediction that he would leave his friends, Harry pointed out that it meant Dumbledore knew he would always want to come back.