Power screwdrivers install and remove screws with greater speed than manual screwdrivers and greater precision than drills. They have a chuck that holds interchangeable screwdriver bits and a motor that rotates the bits to turn screws without overdriving them, snapping them, or stripping the screw head. Corded screwdrivers plug into an outlet to allow longer run times than cordless screwdrivers for applications where portability isn't a concern. Cordless screwdrivers run on batteries, so they are more portable than corded screwdrivers and allow use where a wired power source is unavailable.