Marlinespike - Hitches - Sheepshank
A sheepshank can be used to shorten a length of rope or to take the strain off a worn area of rope. The worn area must be in the center turn of the knot so that the tightened outer turns bear the weight.
Start with three crossing turns that are all in the same direction. Pull the left center crossing (L) through the middle of the left crossing turn from the front, while pulling the right center crossing (R) through the middle of the right crossing turn from behind.
Pull on the loops you just formed and then on the standing parts so that the outer crossing turns tighten around the loops.
This knot will only hold when strain is applied to the standing ends. If the line becomes slack, the outer crossing turns will loosen and the knot will fall apart.
Sheepshank Man o' War
More secure, and certainly more decorative, than the sheepshank, this version starts with four overlapping crossing turns (all in the same direction).
Pull the right center strand (R) through the right outer turn from back to front and the left center strand through the left outer turn from front to back.