A study of physical actions and spatial relationships are explored between a human and the action of sitting on a stool. An ergonomic analyses of the human form while sitting on a stool is used to identify an issue of poor posture, which is to be solved by a performative, tectonic language at a wearable scale. Through rigorous research, documentation, and analysis, it was determined that a tennis ball wedged between the spine and chair backrest created a sensation of pressure causing the user to realign their spine. This became the basis of the Tennis Ball Spinal Aligner, a prosthesis fabricated from recycled wood blinds and tennis balls, that sought to adjust incorrect sitting posture.