The significant difference between both styles is the cut and also form of the bags. The mummy bag is extra restricting. You can think about it like your own individual cocoon where you can go to bed in the evening as a caterpillar as well as wake up the next early morning as a butterfly. You're completed tight with not a lot of area to relocate. The rectangle-shaped bed on the other hand gets its name from its rectangle-shaped form as well as lets you relocate your legs.
Semi-Rectangular: I call this the cross. This backpacking bag is rectangle-shaped ahead and afterwards slenders along towards the feet. With this type, you obtain added space, but not as much weight as a true rectangular resting bag. For those who are claustrophobic, like me; we can reach sleep a little better inside a bag with added room in it and still have some benefit from the form.
In 1917 the zipper was developed and, of course, these made for a terrific seal for the rectangular sleeping bags allowing an individuals body warmth to remain trapped longer consequently keeping them warmer on those cold winter season evenings. Basically the term resting bag essentially suggests a safety bag for someone to rest in.