Returns or sets the thickness of the specified line, in points. Read/write Single.
Example
This example adds a green dashed line two points thick to myDocument.
Set myDocument = ActivePresentation.Slides(1)
With myDocument.Shapes.AddLine(10, 10, 250, 250).Line
.DashStyle = msoLineDashDotDot
.ForeColor.RGB = RGB(0, 255, 255)
.Weight = 2
End With