Pantographs are usually made from four aluminum arms that are attached at various points.
The arms form two "V" shapes, with one "V" upside down. They are attached so that each arm is parallel with one other arm. The attachments at the bottom of each "V" are permanent. The other attachments are adjustable.
The two "V" shapes are attached so that they can pivot off each other. This is the mechanism that facilitates the to-scale duplication. Changing the points at which the arms connect is what determines the scale, and whether the new document will be smaller or larger than the original.
Place a piece of paper under the end of the pantograph that has a writing implement attached. With the anchor end, the user traces the original document.
The pantograph will facilitate a to-scale change so that the drawing that occurs with the writing implement is identical to the original, except for size.