Prepared as lines only. Some may be cut while others represent seams and gaps. This method allows printing onto coloured card.

When a CNC card cutter, basically a plotter is used the lines may be plotted before the outline is cut out.
This demonstrates the outline only as plotted.

Windows would be cut out while the seam lines would appear on a coloured card back ground.
Outlines for seams etc. plotted onto a silvered car. This example was plotted and cut on a Sihouette Cameo machine. Below the three car model.
Outlines for seams etc. this example was printed using an inkjet print. printed alignment marks mean it can be cut out on a Sihouette Cameo machine.