According to a rundown of the brushes, on this forum:
SnakeHook: This brush pulls an extrusion out from the underlying surface. The slider value determines how an extrusion angles away from the surface from which it is pulled. A low value will cause the extrusion to be pushed backward (into the screen) as it is pulled out. A value of 0 will cause the stroke to pull perpendicular to the original surface, and a high value will pull toward the user.
I believe this to be wrong. Slider=100 seems to pull out perpendicular to the original surface.
-Sterling