Chester is leafing, threateningly, through a thick phone book when Fitz tells him it is used to beat people because it leaves no marks. The writers have it half right. Rubber hoses were used to beat folks anywhere on their body, a lot of pain with no bruising to indicate abuse. But a heavy phone book was only used to whack straight down on the top of a person's head. That compressed the vertebral disks in the the neck and caused astounding pain while leaving no mark.