Lark's Head Knot

A Lark's Head Knot (also known as a "Cow Hitch") is used to attach beam sticks to your cloth and warp beams and/or attach warp ends to either the beam sticks or warp extenders (in the case of floor looms). You can also use this knot to tie warp threads onto the beam stick of the cloth beam as shown here:

This is how to make one: