Reply To: Box lines listed on Special Symbols page.
I believe this is on the errata list. For now, here's my recommendation.
Just as a single symbol is not a box line, 3 of them isn't a box line either. I would NOT use this option. I would list the box lines as shown in Formats with the single symbol and add the description that you have suggested "box lines go across the page" for both top and bottom box lines and any other box lines that may be necessary.
--Joanna