PenLineCaps Flat and Square values

Question

Illustrate the basic difference between the PenLineCap's Flat and Square values?

Answer 1

Flat line cap ends precisely on the endpoint, while a Square line cap expands beyond the endpoint. Alike to the Round line cap, you can suppose a square with similar dimensions as the Pen's Thickness centered on endpoint. Thus, the line ends up expanding half length of the Pen's Thickness.