What does Keep her kings in the back row mean The Catcher Rye?

The phrase "keep her kings in the back row" in The Catcher in the Rye is part of a conversation regarding an imaginary game called Checkers. However, the novel uses the game of Checkers as an allegory for real life. The phrase could be interpreted as advice to approach delicate or dangerous matters with caution, perhaps even by being reserved or holding back certain abilities or resources until they are truly necessary or the time is right. It could also suggest using a low profile to keep others at bay or avoid becoming the center of attention in certain situations.