Saws are circular and have eight sharp curved spikes pointing out of them. In the middle of the saw is a circle.
Saws will come out of the top left part of the screen. They will move fast around the edges of the screen, and when coming out of the side of the screen, they will come in groups of five or so. They will not destroy other enemies.
The easiest way to destroy a saw is to go to the right side of the screen and repeatedly shoot. They can be destroyed pretty easily this way, as they will sustain damage quickly as they come down to the ground.