The Winding Cross Backpack is a back tying technique, usable from sitting age of your child. The baby is positioned on your back, but not very high. The baby is fixed with a 3-layer tying technique. Here one strand runs diagonal, the other one runs across.
Unlike with the simple backpack you lead the sling strands through UNDER the arms first and then OVER the shoulders. This relieves the shoulders, especially with larger children.
Pictures (Click on the picture to see the sling):