The Standard Bobbin Holder is basically a glorified coat hanger, but... It mounts to the stem of the vise by squeezing it open a bit and sliding up the stem.

It grips in place and can be height adjusted simply by squeezing to open and then moving. It is a fixed length away from the head/jaws.

A very discreet and simple, but extremely practical spool holder that allows you to free both hands, which you need, for example, when tying flies or more complex tying techniques.