This position is used to put on slave bracelets for chaining the slave.
A common place to chain slaves is to their Master's bed or at a Tavern there are rings in the walls that a Master may use to attach a slave to while he goes about his business.

Book 8, page 146
A binding postion. The slave turns her hips slightly to the side. Her back and shoulders are held erect, arms sweeping around her body to cross at her wrists in the small of her back, her head lifted it turns to the left. The slave is now positioned to have slave bracelets fastened at her wrists.

"Bracelets," he snapped. She put her head in the air and placed her hands behind her back.