In bondage terminology, a hammerlock means tying an arm so that it is held behind the person's back with the hand pulled as near as possible to the person's neck or shoulder. In a double hammerlock, both arms are in a hammerlock, generally with the wrists tied together. Do not try this method unless you are either flexible (you must be able to easily put your hand between your shoulder blades without any help).
Put on you favourite fetish clothes and desirable bondage. In the example below, I was wearing:
You need a high anchoring point you can tie a rope with a cinching loop on the other end to (stairs in this example). Do not tie the rope directly, use an ice padlock in between, so when the ice has melt down, you will be able to lower your hands and use a knife (you left somewhere around) to cut through the loops.
Karada is a very important part here, because the upper part of it will be used as one of the anchoring points. Pass the rope with the cinch loop through the ring tied to the neck part of the karada or just through the upper most karada loop on the back of your neck.
This is the current scheme (from top to bottom):
The cinch loop should be in between your shoulder blade and the small of your back. Use the loops just like you always use them and tug on the rope to cinch the noose. You hands are bound behind your back
Now if you slowly sit down, your bound hands will be drown towards your neck forming the double hammerlock. Do that SLOWLY, to let your arms the chance to adapt and let your body keep balance. If your legs and knees are bound together (you have to do in advance, of course), and if you stay on your knees, it will be extremely difficult to stand back up. Wearing high heels lowers this possibility even further.