What is Forge?

Legal Definition
A forge is a type of hearth used for heating metals, or the workplace (smithy) where such a hearth is located. The forge is used by the smith to heat a piece of metal to a temperature where it becomes easier to shape by forging, or to the point where work hardening no longer occurs. The metal (known as the "workpiece") is transported to and from the forge using tongs, which are also used to hold the workpiece on the smithy's anvil while the smith works it with a hammer. Sometimes such as when hardening steel or cooling the work so that it may be handled with bare hands; the workpiece is transported to the slack tub, which rapidly cools the workpiece in a large body of water. The slack tub also provides water to control the fire in the forge.
-- Wikipedia
Legal Definition
To fabricate, construct or prepare one thing in imitation of another thing, with the intention of substituting the false for the genuine or otherwise deceiving and defrauding by the use of the spurious article. To counterfeit or make falsely. Especially, to make a spurious written instrument with the intention Of fraudulently substituting it for another or of passing it off as genuine; or to fraudulently alter a genuine instrument to another's prejudice; or to sign another person's name to a document, with a deceitful and fraudulent intent See In re Cross (D. C.) 43 Fed. 520; U. S. v. Watkins, 28 Fed. Cas. 445; Johnson v. State, 9 Tex. App. 251; Longwell v. Day, 1 Mich. N. P. 290; People v. Compton, 123 Cal. 403, 56 Pac. 44; People v. Graham, 1 Sheld. (N. Y.) 155; Rohr v. State, 60 N. J. Law, 576, 38 Atl. 673; Haynes v. State, 15 Ohio St 455; Garner v. State, 5 Lea, 213; State v. Greenwood, 76 Minn. 211, 78 N. W. 1042, 77 Am. St. Rep. 632; State v. Young, 46 N. In 266, 88 Am. Dee, 212.

To forge (a metaphorical expression, borrowed from the occupation of the smith) means, properly speaking, no more than to make or form, but in our law it is always taken in an evil sense. 2 East, P. C. p. 852, c. 19, ยง 1.

To forge is to make in the likeness of something else; to counterfeit is to make in imitation of something else, with a view to defraud by passing the false copy for genuine or original. Both words, "forged" and "counterfeited," convey the idea of simllitude. State v. McKenzie, 42 Me. 392.

In common usage, however, forgery is almost always predicated of some private instrument or writing, as a deed, note, will, or a signature; and counterfeiting denotes the fraudulent imitation of coined or paper money or some substitute therefor.
-- Black's Law Dictionary
Legal Definition
To commit forgery; to counterfeit.
-- Ballentine's Law Dictionary