King your pieces
Rules to play Checkers
To crown your piece to make it king, simply place one of your own captured pieces on top of it, so its easily distinguishable because of its height. The king can still only move horizontally on the black squares, but he can move forward and backward, so its easier for the king to capture the opponents checkers.
Kings can still only move one diagonal space at a time during a non capture move. However, when a king is capturing checkers, it can move forward and backward on the same turn.
Some checkers sets have a crown on the back of the checkers, so you can just flip a piece over once its crowned to designate it as the king instead.
There is no limit to how many crowned pieces you can have.