A "guitar pick" or "plectrum" is a small piece of hard material generally held between the thumb and first finger of the picking hand and is used to "pick" the strings. Though most classical players pick with a combination of fingernails and fleshy fingertips, the pick is most often used for electric and steel-string acoustic guitars. Though today they are mainly plastic, variations do exist, such as bone, wood, steel or tortoise shell. Tortoise shell was the most commonly used material in the early days of pick-making, but as tortoises and turtles became endangered, the practice of using their shells for picks or anything else was banned. Tortoise-shell picks made before the ban are often coveted for a supposedly superior tone and ease of use, and their scarcity has made them valuable.
Picks come in many shapes and sizes. Picks vary from the small jazz pick to the large bass pick. The thickness of the pick often determines its use. A thinner pick (between 0.2 and 0.5 mm) is usually used for strumming or rhythm playing, whereas thicker picks (between 0.7 and 1.5+ mm) are usually used for single-note lines or lead playing. The distinctive guitar sound of Billy Gibbons is attributed to using a quarter or peso as a pick. Similarly, Brian May is known to use a sixpence coin as a pick, while noted 1970s and early 1980s session musician David Persons is known for using old credit cards, cut to the correct size, as plectrums.
Thumb picks and finger picks that attach to the finger tips are sometimes employed in finger-picking styles on steel strings. These allow the fingers and thumb to operate independently, whereas a flat pick requires the thumb and one or two fingers to manipulate.