Redhawk
Mechanical BH's have the blades tucked into the ferule and will open open on the impact. Many archers will use these instead of a fixed blade head because they can get them to fly the same as their fieldpoints.
The fixed blades are just that! They are inset in the ferule and lock into place when you tighten the head down. The blades are exposed to the wind and could steer your arrow if the bow isn't tuned properly! Hope I helped a little
AL