Bump stocks are modifications to guns like the AR-15 and AK-47-style weapons Paddock used that take advantage of a rifle's recoil to allow a shooter to pull the trigger far faster than a human could ordinarily do. The shooter pushes forward with his non-trigger hand (usually on some kind of forward grip), and the bucking of the weapon against his shoulder causes his finger to depress the trigger multiple times per second. That's why recordings of the gunfire at the Las Vegas massacre sound like machine gun fire, not someone pulling the trigger repeatedly. There is no practical civilian application for such a thing. It would be useless in hunting, self defense or target shooting because it makes the weapon hard to control and nearly impossible to aim. About the only thing it's good for is firing indiscriminately into a crowd. We should absolutely ban them and similar devices, like trigger cranks, which achieve a similar effect.