Contour scribing is cutting a piece of wood, usually the side of a cabinet, to match the side of a wall. The wall can be rock, tile, Sheetrock or any composite material that is not flat or square. A small tool called a scribe is used to transfer the layout of the wall to the side of the cabinet wood. A circular saw is used to cut the contour of the wall onto the side of the cabinet so it fits tight against the wall.
Place the cabinet in place against the wall as if it were already installed. The wood to be scribed on the cabinet should be flush against the wall, touching the wall.
Hold the scribe tool in between your thumb and index finger at the top point where the wood meets the wall. The scribe tool is just like a compass--without the sharp point. It has a pencil on one side, and a small metal arm on the other side. The pencil side should be touching the cabinet; the metal arm should be touching the wall.
Slide the scribe tool down the wall, allowing the small arm to follow the wall as the pencil draws the line, transferring the wall's contour to the wood on the cabinet.
Remove the cabinet from the wall. Turn it on its side so that the scribed line is facing up. Use a skill saw to cut the contour of the wall onto the wood on the cabinet.
The example described is for wood scribing on cabinets, where the majority of contour scribing is performed. You can scribe individual pieces of wood exactly the same way.