xlBordersIndex

Specifies the border to be retrieved.

xlDiagonalDown	Border running from the upper-left corner to the lower-right of each cell in the range (5)
xlDiagonalUp	Border running from the lower-left corner to the upper-right of each cell in the range (6)
xlEdgeBottom	Border at the bottom of the range (9)
xlEdgeLeft	Border at the left edge of the range (7)
xlEdgeRight	Border at the right edge of the range (10)
xlEdgeTop	Border at the top of the range (8)
xlInsideHorizontal	Horizontal borders for all cells in the range except borders on the outside of the range (12)
xlInsideVertical	Vertical borders for all cells in the range except borders on the outside of the range (11)

xlDiagonalDown

Border running from the upper-left corner to the lower-right of each cell in the range (5)

xlDiagonalUp

Border running from the lower-left corner to the upper-right of each cell in the range (6)

xlEdgeBottom

Border at the bottom of the range (9)

xlEdgeLeft

Border at the left edge of the range (7)

xlEdgeRight

Border at the right edge of the range (10)

xlEdgeTop

Border at the top of the range (8)

xlInsideHorizontal

Horizontal borders for all cells in the range except borders on the outside of the range (12)

xlInsideVertical

Vertical borders for all cells in the range except borders on the outside of the range (11)

REMARKS

* If you are creating styles in C# and you want to include a border, then the following 4 constants must be used:
* Excel.Constants.xlBottom (-4107) instead of Excel.xlBordersIndex.xlEdgeBottom
* Excel.Constants.xlTop (-4160) instead of Excel.xlBordersIndex.xlEdgeTop
* Excel.Constants.xlLeft (-4131) instead of Excel.xlBordersIndex.xlEdgeLeft
* Excel.Constants.xlRight (-4152) instead of Excel.xlBordersIndex.xlEdgeRight
* The xlBorderWeight specifies the weight of the border around a range.