Used on heads of 3/4" and 5/8" dia. bolts to keep bolt from turning as nut is being tightened. Extremely useful on rural ridge pin type construction— outer edges of wrench are tapered so that they can be wedged between flanges on channel and bolt head to keep bolt from turning.
Place over the heads of 0.75 in (19 mm) and 0.625 in (15 mm) diameter bolts to keep bolt from turning as nut is being tightened