The principle stone or marble (in a game); shooter.
In playing with marbles it is the one flicked at (or shot at) the others. In the game simpan (jacks played with real stones) it is the stone thrown into the air. In hopscotch it is the stone that marks a certain place.
This marble is good to be made the pricipal one.
This round stone I will make the shooter when I play jacks.