information:extraction, linguistic:paraphrasing
Stretching

After soaking in water to make the skins workable, the skins were placed on a stretching frame. A simple frame with nails would work well in stretching the pelts. The skins could be attached by wrapping small, smooth rocks in the skins with rope or leather strips. Both sides would be left open to the air so they could be scraped with a sharp, semi-lunar knife to remove the last of the hair and get the skin to the right thickness. The skins, which were made almost entirely of collagen, would form a natural glue while drying and once taken off the frame they would keep their form. The stretching aligned the fibres to be more nearly parallel to the surface.