This function is only available when 1 or more features are selected. It operates differently depending on the number of features selected:
a) If one feature is selected (the current feature): you will be prompted to confirm that all displayed features in the terrain file which cross the current feature will be split at the intersecting points. You may also check the box to include hidden features, before pressing OK.
b) If more than one feature is selected, then only the selected features are split at the intersecting points with the current feature.
When this operation is complete, all broken features to the right of the current feature remain selected. This implies that if the current feature is a closed polygon oriented clockwise, then the broken features inside the polygon will be selected.