interesting article on Islam the rod and woman
http://www.tulipgirl.com/mt/archives/000107.html

"The [wife-]beating must never be in exaggerated, blind anger, in order to avoid serious harm [to the woman]." He adds, "It is forbidden to beat her on the sensitive parts of her body, such as the face, breast, abdomen, and head. Instead, she should be beaten on the arms and legs," using a "rod that must not be stiff, but slim and lightweight so that no wounds, scars, or bruises are caused." Similarly, "[the blows] must not be hard."