Night Bivouac Lock

Darkness dropped across the capstone, cutting off visual readings from the feather array and the brass gear sundial. Night operations require sealing the perimeter. I stepped back along the stone ledge to my sardine tin shelter beneath the overhang. A discarded copper safety pin lay wedged in a dry crack nearby. Gripping the spring coil with both gloved hands, I drove its pointed pin horizontally into the mortar joint flanking the tin entrance, leaving the brass loop projecting across the threshold. I then slotted a flat piece of dry cedar bark behind it, securing the door slot against rising drafts. Boots set on stone, the outpost is fortified.