StrokeCap Inherits: Enum Styles to use for line endings. Properties BUTT – Begin and end contours with a flat edge and no extension. ROUND – Begin and end contours with a semi-circle extension. SQUARE – Begin and end contours with a half square extension. Properties# BUTT = 'butt' # Begin and end contours with a flat edge and no extension. ROUND = 'round' # Begin and end contours with a semi-circle extension. SQUARE = 'square' # Begin and end contours with a half square extension.