A dolly is the name given to a category of tools used in shaping sheet metal. In general, a dolly is a solid piece of metal, small enough to hold in one hand, with a curved or shaped face. Generally a dolly will have more than one surface, each with its own radius of curvature (much like a three-dimensional French curve

French curve

A French curve is a template made out of metal, wood or plastic composed of many different curves. It is used in manual drafting to draw smooth curves of varying radii....

), allowing the craftsman more flexibility in using the tool.

A dolly can be used either as a hammer

Hammer

A hammer is a tool meant to deliver an impact to an object. The most common uses are for driving nails, fitting parts, forging metal and breaking up objects. Hammers are often designed for a specific purpose, and vary widely in their shape and structure. The usual features are a handle and a head,...

, shaping the metal to match the curve of the dolly, or as small anvil

Anvil

An anvil is a basic tool, a block with a hard surface on which another object is struck. The inertia of the anvil allows the energy of the striking tool to be transferred to the work piece. In most cases the anvil is used as a forging tool...

 to provide a curved surface over which to dome or dish metal. They are commonly used to shape sheet metal in auto repair, especially in locations where it is difficult to swing a hammer.

They can also be used as backers for upsetting metal. When used as a portable anvil, a dolly can be used to hold a rivet

Rivet

A rivet is a permanent mechanical fastener. Before being installed a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite the head is called the buck-tail. On installation the rivet is placed in a punched or pre-drilled hole, and the tail is upset, or bucked A rivet...

 in position while it is being clenched with a "snapper". Such dollies are commonly cylindrical in shape, and rely on mass

Mass

Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...

 to work. The act of using it is known as holding up or holding on. Dollies can also be used in boat building

Boat building

Boat building, one of the oldest branches of engineering, is concerned with constructing the hulls of boats and, for sailboats, the masts, spars and rigging.-Parts:* Bow - the front and generally sharp end of the hull...

, when clenching nails. See clinker (boat building)

Clinker (boat building)

Clinker building is a method of constructing hulls of boats and ships by fixing wooden planks and, in the early nineteenth century, iron plates to each other so that the planks overlap along their edges. The overlapping joint is called a land. In any but a very small boat, the individual planks...

.