Jack stands are sturdy devices used to support a vehicle after it has been lifted with a jack. They provide a stable base to ensure safety while working underneath the vehicle. Typically made of metal, jack stands come in various heights and weight capacities to accommodate different vehicles. To use jack stands, first lift the vehicle with a floor jack or bottle jack and then place the stands under the vehicle's designated support points. Once positioned, lower the vehicle onto the stands, ensuring they are securely in place before starting any maintenance or repairs.