Shaft skin is the skin which covers and protects the parts of the penis shaft. The shaft skin is part of the epithelium of the penis. The shaft skin incorporates a layer of muscle fiber called the Dartos.
In humans and some other mammals parts of the shaft skin become covered with pubic hair at puberty.
Note: The foreskin is not part of the penile shaft skin but a separate "organ" which covers and protects the glans penis. The shaft skin, the foreskin and the preputial mucosa build the epithelium of the penis.