A poor girl was force to stretching her body with an armbinder forcing her arm in a strappado position and a spreader bar that would force her legs apart. A nice red ballgag which was force into her mouth to muffle all her complains.
If the girl was trying to raise her head, the crotch rope will be tighten, her arm will be pull further upwards and will trigger a mechanism in the spreader bar which will start to extend the bar which forcing her legs to spread out more.