In standard checkers rules you can only crown a piece as a King once. When this happens a piece is double stacked and it can move forwards as well as backwards one space at a time. Variations of the checkers rules exist where you can turn a piece into a triple or even quadruple King when these pieces reach opposite sides of the board three or four times. These pieces have improved attacking moves, better movement and the ability to jump friendly pieces. But this isn't in the standard rules.