2.1.130 Part 4 Section 2.4.3, bottom (Table Cell Bottom Border)
WordPad supports this element. WordPad does not support the following attributes of this element: frame, shadow, space, themeColor, themeTint, and themeShade. WordPad supports the color attribute for all values except "auto". WordPad treats "auto" as "black". WordPad treats all values of the val attribute as "single". When the document is loaded, WordPad shows borders of all table cells, even when the size specified in the sz attribute is "0". For borders whose sz attribute is "0", WordPad shows a light gray border. When the document is saved, WordPad writes all borders of a table cell. The original value of sz is roundtripped, but the value of the color attribute is written as "black" if no value is specified.