g.DrawLine(Pens.Black,60,20,60,100) draws a line from (60,20) to (60,100)
of the Graphic g.
We can control the thickness of the line and the end-cap.
The cap determines what happens at the end of a line.
Thickness and CAP style
We draw three thick black lines. Each has thickness 15. The System.Drawing.Drawing2D.LineCap can take many values See http://msdn.microsoft.com/en-us/library/system.drawing.drawing2d.linecap.aspx