The Sea to Summit Sentinel Footprint adds a layer of 68D waterproof fabric between the tent floor and rough or wet ground, protecting against abrasion and tears the Sentinel's already-waterproof floor would otherwise take on directly. Hypalon attachment points engage the poleset tips, so the fly can go up first and the inner tent stays dry underneath during setup in active rain. The same connection supports a Fly Only pitch for trips where a full shelter isn't worth the extra weight. What Our Gearhead(R) Experts Are Saying:"I pitched the fly first during a storm that started before I even had the poles together, and the inner tent came out of the bag completely dry once I clipped it in underneath. Breaking camp the next morning in the same rain worked the same way in reverse."