Before applying the obstetrical chains to "pull" a calf during a difficult birth, a proper analysis of the situation must be made. Wash the vulva, anus and the area in between using soap and warm water. Pulling on a calf should only be done when the presentation and posture of the calf are normal. Normal is defined as the "anterior presentation" with fore feet first, head resting on the limbs, and the eyes level with the knees. A backwards calf can be delivered only when both back limbs are presented. Before chains are applied, be certain that the cervix is completely dilated.
To properly use obstetrical chains when assisting with a difficult birth, follow the this procedure. To attach the chain, loop it around the thin part of the leg above the fetlock. Then, make a half hitch and tighten it below the joint and above the foot. Make certain that the chain is positioned in such a manner that is goes over the top of the toes. In this way the pressure is applied so as to pull the sharp points of the calves hooves away from the soft tissue of the vaginal wall. (The toes of the backwards calf will be upside-down compared to the forward presentation).
Obtain a copy of "Calving Time Management of Beef Cows and Heifers" E-1006, an OSU Extension Circular that thoroughly discusses working with cows and heifers before and during calving season. It can be downloaded from: http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-9389/E-1006web2014.pdf