Cross section Plotting

In MX, when taking sections, you cannot have a vertical face in the section, as there is nothing to tell which string should be picked up first. Note that MX does allow you to design strings vertically above each other.

Think of a road cross section - left top of kerb, left carriageway, centreline, right carriageway, right top of kerb. If you say top of kerb comes first, the section will be - LTOK, LCWY, CLNE, RTOK, RCWY - incorrect. If you say carriageway comes first, you get LCWY, LTOK, CLNE, RCWY, RTOK - incorrect. To solve this problem, design the LTOK to be 2mm to the left of LCWY, and RTOK to be 2mm to the right of RCWY - this will ensure that you cross section works correctly. This is also true when triangulating.

In your case, just offset the strings slightly, and your sections will work.