Double folded construction provides extra rigidity The knuckles on both ends are crimped to prevent the pin from being removed The hinge pin does not occupy the crimped knuckles on both endsWARNING: This product can expose you to chromium, nickel, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, go to www.P65WARNINGs.ca.gov.