Shingling was a stage in the production of bar iron

Wrought iron

thumb|The [[Eiffel tower]] is constructed from [[puddle iron]], a form of wrought ironWrought iron is an iron alloy with a very low carbon...

 or steel

Steel

Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

, in the finery

Finery forge

Iron tapped from the blast furnace is pig iron, and contains significant amounts of carbon and silicon. To produce malleable wrought iron, it needs to undergo a further process. In the early modern period, this was carried out in a finery forge....

 and puddling processes. As with many ironmaking terms, this is derived from the French - cinglage.

The product of the finery was a bloom or loop (French loup); that of the puddling furnace was a puddled ball. In each case, this needed to be consolidated to a more regular shape. This was done using a power hammer

Power hammer

Power hammers are mechanical forging hammers that use a non-muscular power source to raise the hammer preparatory to striking, and accelerate it onto the work being hammered...

, worked either by a waterwheel or steam. In the finery, this was part of the work of the finer; in puddling, it was done by a special workman called the shingler. The iron (or steel) then had to be drawn out under the hammer or rolled in a rolling mill to produce a bar. In more recent times, the process has been carried out using mechanical jaws to squeeze the puddled ball into shape.