The starting area is called the "Throwing Area", and it has at the front lip, a raised block called the "Trig".
Figure below from http://www.nasgaweb.com/rules.asp
The Throwing Area is 4'6" wide, and has 2 depths.
The first is the shorter, 7'6" for the Stone throws.
The second depth is 9' even, a little more room for the Weights over Distance.
The Hammers must be thrown from a stationary position inside the Throwing Area.
Weight over Distance with The Trig in action!!
Photo credit: http://driveaway.files.wordpress.com/2010/03/lrg-29-ryan1.jpg