Duct tape's combination of strength, adhesion, waterproofing, and flexibility makes it irreplaceable in survival scenarios. A torn waterproof jacket in a Scottish downpour, a split tent pole on a windswept campsite, a cracked water bottle, or a flapping sole on a walking boot — duct tape handles them all as an immediate field repair. Beyond gear repair, it serves medical purposes: closing wound edges, securing splints and dressings, and even fashioning butterfly strips in an emergency. You can carry several metres wrapped flat around a credit card, adding virtually no weight to your kit.