Door handle is an ambiguous term, and includes door latches, bars, and knobs. Depending on the geographical location and its place in time, they vary in design, form and materials. The only constant is its function: an attachment used to open or close a door.Knobs and handles functionsThe earliest doors extant are approximately 5000 years old. Door handles, as devices to manipulate a gateway, became a necessity shortly after the invention of the pivoting mechanism. To most, pivots are simply known as hinges, however, there are nearly as many hinge designs and configurations as there are handles.The simplest handle is a pull - or push - projection on the side opposite the hinge. The placement of the handle is generally where it will provide an optimal mechanical advantage; most doors operating as second class levers. Doors with centre pulls or rings, or a pivot point in a location other than one edge of the door, use first or third class lever principles.hollow stainless steel lever door handleDepictions of door handles in paintings dating to the first century CE are centrally placed hinged rings. The modern door knocker is a vestige of this style of primitive door handle. Doors were typically secured by bars and brackets to prevent them from being opened by either intent or accident.Knobs with latches and barsOver time, large crossbars used to secure a door were supplanted by sliding bars, operated by a handle secured to the bar and projecting through a slot in the door, or as a pivoting bar - often called a latch - that could be dropped into a matching slot on the door jamb. In Colonial America, the operating mechanism for a small pivoting bar was a latch string threaded through a hole in the door near the handle. There are - probably apocryphal - accounts and references implying that this mechanism was a workaround for heavy taxes and a crown edict mandating the colonists could only use door latches or locks imported from England.About the middle of the 18th century, handles and locks were integrated into a single unit, the earliest known examples being levers that both operated the latch and served as a pull to open the door.Knobs and handlesThe handle, as it exists today, is a relatively new invention dating to the mid-19th century, with the first American patent dated in the 1850s. Handles and knobs experienced a massive period of growth and development throughout the Victorian Era (1830-1900). Thousands of variations on the theme of the door handle, in combination with modern production methods, made door handles accessible to virtually everyone. Latches faded in popularity and use, relegated to service in barns and similar outbuildings where their simplicity and design function trumps external appearance.To most Americans, the terms handle and knob are synonymous. In Europe, however, door levers constitute the vast majority of door handles. Because of their utility and accessibility, door levers are gaining popularity in the United States. They are far easier for an individual physically challenged by arthritis, disease or injury to operate than round door knobs. While exterior and large door handles will eventually be supplanted by automatic opening mechanisms, door handles will continue to necessary for smaller doors on interior doors, cabinetry and other furniture for centuries to come.