Hammock Underquilt and Overquilt for Camping, hammocks. When the temperature drops, you can still hang and enjoy the outdoors and stay warm. Grand Trunk is based in Salt Lake City. Each product comes with our amazing support and a lifetime warranty. We’ve been making hammock for over 20 years. Use the Thermaquilt as a Sleeping Bag too. It’s a summer bag rated to 40 degrees. Filled with quality synthetic fill that is machine washable and packs down small.