Porcelain prop, high fire ceramic fibre is for supporting porcelain during firing. Use this to prop and support your porcelain bisque pieces when firing to help prevent sagging or sticking.
You may form and place it in area needing support during firing, such as wings and tails of birds, limbs of trees, around flower petals, etc.
Also use between box lid and box to keep them from sticking together during firing. Also stuff porcelain prop in doll head to avoid warping during firing. Place dome-heads upside down on porcelain prop to avoid warping.