The professional car (quoted from a leading trade association) "is loosely defined as a custom-bodied vehicle, based on passenger car styling, and used in the funeral, rescue or livery services." Such vehicles may be ambulances, funeral cars (hearses, flower cars, service cars), limousines, or combination cars, vehicles specially built to combine multiple functions (hearse-ambulances, sedan ambulances or invalid coaches). From the 1930s to the 1970s, a common starting point for such vehicles was the Cadillac Commercial Chassis (or similar vehicles); using a heavy-duty frame, the vehicle was a bare chassis aft of the dashboard, leaving all exterior and interior bodywork to be completed by coachbuilders (much of the vehicle was completed by hand).