The standard convention for labeling contours is to knockout the line behind the label. Obviously we could cut each line and delete it, but in a small scale mapping project this would not be very efficient. In Illustrator, it is much faster to use a clipping mask to style all the contour labels. And thanks to a few tips from my friends at NACIS, it’s quick and easy. Here is a link to the text version, along with a little video tutorial.