The video demonstrates creating a three-step winder box in SolidWorks to turn a staircase 90 degrees. It explains design strategy, layout sketches, and reference planes for stability, using global variables for easy updates. The process includes modelling winder steps, applying cuts for newel posts, and building upper and lower stringers with joinery details like rebates and hidden tenon joints. Boolean operations simplify machining geometry, while patterns handle risers, treads, and wedge cuts. The model is fully parametric, allowing adjustments to height, landing distance, and rise via the Equation Manager, ensuring flexibility and efficient staircase design.