How to: Use a Pen to Draw Rectangles
The following example draws a rectangle with its upper-left corner at (10, 10). The rectangle has a width of 100 and a height of 50. The second argument passed to the Pen constructor indicates that the pen width is 5 pixels.
When the rectangle is drawn, the pen is centered on the rectangle's boundary. Because the pen width is 5, the sides of the rectangle are drawn 5 pixels wide, such that 1 pixel is drawn on the boundary itself, 2 pixels are drawn on the inside, and 2 pixels are drawn on the outside. For more details on pen alignment, see How to: Set Pen Width and Alignment.
The following illustration shows the resulting rectangle. The dotted lines show where the rectangle would have been drawn if the pen width had been one pixel. The enlarged view of the upper-left corner of the rectangle shows that the thick black lines are centered on those dotted lines.