It's all in the name and the name is, Awl

Awl is a pointed object that pierces and pierce through sand is what these snakes do. They are built to do so. Their pointed snout helps them dip into the sand and thus they disappear in and reappear on the surface of the sand. 
Here is an image of the snake after it popped its head above the surface of the desert sand. 

Sizes:
Small: A4: 11.69 X 8.27 inches
Medium: A3: 16.53 X 11.69 inches
Large: 2 X 3 feet : 24 X 36 inches