Happy Christmas.
Domme showing off her Christmas-themed setup. The sub is
Anne - UK submissive
The bondage device is shown in the inset picture. It's a bar chair fastened down onto a baseboard on which the submissive kneels. Her ankles are fastened to the board, her arms tied round the back of the chair and her neck secured in the cutout in the seat of the chair by the lockable band.
Obviously this is posed for a Christmas pic (although the sub does seem to have a rosy glow to her ass cheeks so some fun was being had!). In normal use, the domme would have her pussy exposed and position herself to hold her pussy against the sub's face and mouth. The sub's head is secured so she can't move it away and pretty much all she can do is move her tongue to pleasure the domme, who can fine tune her own position and use the riding crop to keep the sub motivated. She's stuck there until she's finished her task.