Ancient Painters Putty

Many of the stone walls of Petra were rough uneven and unsightly. To make them look good the workers put heavy amounts of plaster on the walls and drew in the bricks or stone blocks to make the wall look neat. Some of the walls were so uneven that the plaster in places were almost a foot thick. Workmen still do that to some degree. 

I had some work done and notices some big cracks between joints. Their reply was, "That is why they make painters putty." Sure enough they filled the cracks with putty and painted over the error.