From the link in Pax's post:
http://www.activeresponsetraining.net/the-turret-drill
http://www.activeresponsetraining.net/the-turret-drill
I'm pretty sure that should also say "parallel", unless you want to shoot people to the left or right of you.“I teach the student to use the ‘nose point’ by pivoting from the hips so that he points with his nose. By always keeping the weapon locked parallel to the ground and perpendicular to his nose he can hit anything he looks at.”