PolylineTo Row (Geometry Section) [Visio 2003 SDK Documentation]
Contains x and ycoordinates of the last point of a polyline and a polyline formula.
A PolylineTo row contains the following cells.
Cell  Description 

The xcoordinate of the ending vertex of a polyline. 

The ycoordinate of the ending vertex of a polyline. 

The polyline formula. 
Remarks
Lines represented as a Polyline row are equivalent to lines represented as a sequence of LineTo rows, but a Polyline row is more efficient. You can change a PolylineTo row to a LineTo row so you can easily see the shape geometry. To do this, rightclick the PolylineTo row, and then click Expand Row on the shortcut menu.
To change a row type to a PolylineTo row, rightclick the row, and then click Change Row Type on the shortcut menu.