Each belt represents the line along the surface from which the distance between grids is measured. The distance is measured by chords, not curve lengths. You can move the belts along their respective grids to adjust where the distance is measured. Click and drag the belt handles to reposition them.
Note: Clicking a belt handle will slightly nudge the belt position in the respective direction of the handle.
The following image shows repositioning of one belt along the U grid.
