Possible Clues:

• How the commander gets a setback with the stones
• Glass marbles
• The commander gets set up with stones
• Set aga up for shiny stones
• A bit precious, as it's about the way in
• They're used in classified ads
• How the commander gets upset with the stones
• Stones, as it's about a barrier
• Stones when taking entrance money
• As the stones are around the entrance