The Piece of Hair is a puzzle item found in room S14 on the third floor of Brookhaven Hospital in Silent Hill 2. It can be obtained from a box by completing the Louise Puzzle, which is opened after unlocking all four locks.
The box which needs to be unlocked to obtain the piece of hair.
The piece of hair is combined with a bent needle and used in a nearby shower room to fish out an elevator key from a drainage hole. This is an example of an abstract item being used for something other than its intended or obvious purpose, a trait which the series is known for.