Paper-Mache Deception
Using supplies from the Alcatraz art studio (yes, Alcatraz apparently had an art studio), the prisoners created fake paper-mache heads of themselves. While working on their escape, they would put the paper-mache head on the pillow and tuck the covers over it so only the top of the head would be showing.
They did this because in order to escape, they needed to continue drilling even inside the walls, so the paper-mache head would make it seam like the prisoners were still in their cell when the guards came around, when in reality they were in the walls of Alcatraz, digging towards their escape.