Couldn't resist after reading above about the topology of a glove.
The sleeping bag, a poem.
On the outside grows the furside; on the inside grows the skinside.
So the furside is the outside, and the skinside is the inside.
One side likes the skinside inside, and the furside on the outside.
Others like the skinside outside, and the furside on the inside.
If you turn the skinside outside, thinking you will side with that side,
then the soft side, furside's inside, which, some argue, is the wrong side.
If you turn the furside outside, as, you say, it grows on that side,
then your outside's next the skinside, which for comfort's not the right side.
For the skinside is the cold side, and your outside's not your warm side.
And two cold sides side by side are not right-side when side to side!
If you decide to side with that side, turn the topside furside inside.
Then the cold side furside skinside's, beyond all question, inside out!
Herbert George Ponting, photographer on Scott's last expedition.
I'm off now to warp a space ship into a Klein bottle.