Perimeter Calibration

Morning light penetrated the drainage hole above, casting a sharp circular beam onto the moss floor. I stepped out from beneath the clay curve to inspect the perimeter. Directly outside the rim lay a smooth, flat piece of sea glass, weathered frosted blue by moisture and grit. I set my rifle beside my boot and used both hands to slide the translucent fragment into the terracotta entrance. By propping the glass against my wooden clothespeg, the morning sun refracted through the blue pane, casting a muted cyan grid across my shelter floor. Perimeter marked. Sector fortified.