How to Sort Index Contours from a Grid

1. Load the grid into ArcView.
2. Create contours.
3. Select all contours (use the select tool).
4. Press the Query button (the hammer icon).
5. Perform the following query:
   ([Contour].mod(50)=0)
6. Click Create new set.

This will extract every fifth contour if the contour interval is 10.

In the view, choose Convert to Shapefile. Now you have a new theme that is every fifth contour. You can now make it bolder, and "Auto-label" only this one.