Originally Posted by
CliffordK
Some sleeping bags are designed to zip flat (zip open around the toes), and then have two identical (or similar) sleeping bags zip together to make a monster sized bag. Then to pack, just zip apart and pack individually.
Theoretically you could have one thin and one thick bag, and choose which you wish for the top depending on conditions.
Never seen that configuration. All I've seen are left/right-specific bags which zips together at the middle.
With the traditional mummy-style hood, a top/bottom configuration would lead to fairly strange profile at the top.