This action is launched from binding below and on the left. First, it is neccesary to get closer into grappling distance, most probably by switching into priest's special longpoint.
If you are in a grappling distance in priest's special longpoint, you can turn your back to your opponent and wrap both his arms by your sword arm. This doesn't result in a strong hold and the opponent my pull his hands free easily - but only without his weapons. While you are not able to hold his arms firmly, you are able to prevent his weapons from escaping.
You don't have any way to harm the opponent from such hold, as you are turned with your back to him. He also cannot harm you, as both his weapons are trapped. But you have access to the opponent's hands and weapons, and you may use your shield to wrench them out of his hands. This means, that the whole action should be viewed as a disarm.
This action is covered by by play 21