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Spline
From WikiPedalia
A ridge on a surface of a part, usually used to prevent an otherwise circular part from turning. Commonly used on freewheels and cassettes where the sprockets attach.
Many newer bottom brackets use splines where the cranks attach to the bottom bracket spindle. Cartridge-type bottom brackets also use a splined wrench to install and remove the bottom bracket unit.
Some frame tubing has internal ribs to reinforce the tube; these are sometimes also referred to as splines.
