The part of the forearm where skin covers the three bone blades looks similar to a fin on top of a fish.
The bone blades can be either perpendicular to the fore arm or can lay on the forearm with blade tips pointed toward the arm elbow.
Bone blades can be used as a weapon when blades are perpendicular to forearm to stave an opponent.
Bone blades resting on the forearm may act as shields to protect the ulna bone in the forearm. The ulna is one of two bone in a forearm from elbow to wrist.
Nietzschean forearm sleeves have a slit long enough to slip all three bone blade through. The sleeves have fasten along the forearm side opposite of the bone blades.
(c) June 2001: Burton Craddock