Whistle
From Lostpedia
In Tabula Rasa Locke carves a whistle out of wood and uses it to attract Vincent from the jungle where he knows he is as Jack saw him there after first waking up in Pilot, Part 1.
Also, Locke and Boone use the whistle in "Special" to attempt to find Vincent after he ran away. Although they do not find Vincent, they do find Claire for the first time since she was kidnapped.
Analysis
Locke's creation and use of the whistle was used, especially in the first instance, to give the audience an idea of himself and other characters. It sets Locke as the hunter and survivalist. He knows what he is doing and does it without asking or telling anyone.
At the same time, this foils Michael (especially early on) and emphasizes his weak relationship with his son. Michael cannot find Vincent on his own, and he lacks the means or motive to do so. It is Locke's good nature to attempt to improve Michael and Walt's relationship that motivates him to not tell Walt that it was he who found Vincent, and not Michael. This is one of the earliest steps towards Michael and Walt developing a loving relationship.

