Locke carved a dog whistle out of wood and used it to attract Vincent from the jungle. Michael had been trying to find Vincent for Walt, but Locke took it upon himself to find the dog after Jack said he had seen Vincent after he woke up after the crash. ("Tabula Rasa")
Locke and Boone searching for Vincent ("Special")
Later, Locke and Boone used the whistle to attempt to find Vincent after he ran away. Although they did not find Vincent, they did find Claire for the first time since she was kidnapped. ("Special")
