Guitar Picks (or less commonly referred to as plectrums) are basically a small flat tool used to pluck or strum a stringed instrument. Guitar Picks are usually made from a single material and the most common and famous one is of course….Plastic !!… such as Celluloid, Nylon and Delrin, (You can also find other materials which in my own opinion are of the less common variety) These materials are: Rubber, Felt, Wood, Metal, Glass, Tagua (The Nut From The Tagua Palm Tree or Ivory Palm Tree), Stone and (My least favourite for obvious reasons!!) Tortoiseshell. Guitar Picks more often than not have a triangular shape (an acute isosceles triangle to be precise) and they have the two equal corners rounded (the part you hold in your hand) while the third corner is less rounded (the part that is in contact with the strings).