Wax is used on the back side of card stock (business cards work well) used to lift a pattern. The wax avoids the card being torn or ripped when being burnished during this process.
The card stock is slightly dampened,,(give it a lick or two) and layed down on the existing engraving. Then burnished into the pattern. It doesn't take much to produce a perfect embossed image of engraving in the card.
To reproduce the image on another surface,,the wax is again used to cover the new surface. Dotted around with your thumb till covered is the simplest way.
The card pattern is swiped lightly with a charcoal pencil which covers the high embossed lines on the card surface .
The pattern is laid down carefully and very lightly burnished again,,even just lightly gone over with your finger will do. The lines are transfered to the wax covered surface with all the finest of detail ready for cutting.
The patterns are reuseable and simply don't wear out if not abused.
It's just one of many different ways to transfer and/or save engraving patterns and another where some form of wax is involved in the process.
They're not as 'pretty' to look at a smoke or ink pulls,but much more useful IMO.