By default, the AllowHeaderExt property is exHeaderExtUndefined, which indicates that the AllowHeaderExt property of the control specifies how the corners of the pool are combined with the headers of the pool. The HeaderColor(exHeaderVertical) property specifies the background color/visual appearance of the vertical header for the giving pool. The HeaderColor(exHeaderHorizontal) property specifies the background color/visual appearance of the horizontal header for the giving pool. The Background(exPoolHorizontalHeaderBackColor)  property specifies the background color / visual appearance of the top/bottom header of the pool. The Background(exPoolVerticalHeaderBackColor)  property specifies the background color / visual appearance of the left/right header of the pool.

The following screen shot shows how the header is displayed if the AllowHeaderExt property is exCornerEmpty:

The following screen shot shows how the header is displayed if the AllowHeaderExt property is exCornerTopLeftExtHeaderTop Or exCornerTopRightExtHeaderTop Or exCornerBottomLeftExtHeaderBottom Or exCornerBottomRightExtHeaderBottom ( default ):

The following screen shot shows how the header is displayed if the AllowHeaderExt property is exCornerBottomLeftExtHeaderLeft Or exCornerBottomRightExtHeaderRight Or exCornerTopRightExtHeaderRight Or exCornerTopLeftExtHeaderLeft:

The following screen shot shows how the header is displayed if the AllowHeaderExt property is exCornerBottomLeftExtHeaderLeft Or exCornerBottomRightExtHeaderBottom Or exCornerTopRightExtHeaderRight Or exCornerTopLeftExtHeaderTop: