Jury Mast Knot or the Masthead Knot
The Jury Mast knot appears to be an odd little knot, as there does not appear to be any photos of it actually being used as a Jury Mast Rig. According to Ahsley’s the Jury Mast or Masthead knot a loops to to which stays can be attached when Jury rigging is required after damage due to a storm or battle. Page 212
I think that in this day and age, this particular knot is a little overlooked. When tied and the loops are adjusted, the Masthead knot makes and excellent sling. So if for example, you have a heavy boulder or stone, this can then be rolled onto the knot. This then gives you four points from which the stone can be man handled out of the way.