The trapping techniques above work well for filled paths,but what open paths? After all, you can’t apply two different stroke properties to a single path. Instead, you clone the path and make the width of the clone larger or smaller to achieve the spread or choke you want. One of the strokes overprints; the other line knocks out.

Follow these steps to spread an open path.

  1. Draw a rectangle. Create a spot color and fill the rectangle with it.
  2. Draw a path inside the rectangle.Create another spot color and apply it to the path. Do not set this path to overprint.
  3. Select the path and clone it.
  4. Press F10 to display the Stroke palette. Increase the stroke weight of the path by twice the amount of spread you need (remember, PostScript strokes grow out f rom their centers) and check the Overprint Stroke option in the Attributes palette to make the stroke overprint.

That’s all there is to it. The original path knocks a hole in the background rectangle, and the clone of the path spreads to just a little bit beyond the edges of the knockout.

To choke the path, follow these steps.

  1. Draw a rectangle. Create a spot color and fill the rectangle with it.
  2. Draw a path inside the rectangle. Create another spot color and apply it to the line. Set this path to overprint.
  3. Select the path and clone it.
  4. Display the Stroke palette. Decrease the weight of the path by twice the amount of choke you need. Leave the Overprint Stroke option in the Attributes palette turned off.
  5. Use the Direct Selection tool to select the original path. Press Command-Shift-]/Ctrl-Shift-] to bring it to the front.

This time,the cloned path is narrower than the original, and knocks out an area that’s slightly smaller than the original path, creating a choke.