A line ending style, as the LE entry of line, polyline and free text annotations names it.
public enum PdfLineEnding
ISO 32000-2 §12.5.6.7, Table 179. A name the table does not list reads as None, as viewers draw it.
kind:method, kind:property, kind:ctor. Press Esc to clear.ButtButt (PDF 1.5): a short line at the endpoint perpendicular to the line.CircleCircle: a circle filled with the interior colour.ClosedArrowClosedArrow: two short lines meeting in an acute angle, closed and filled with the interior colour.DiamondDiamond: a diamond filled with the interior colour.NoneNone: no line ending (the default).OpenArrowOpenArrow: two short lines meeting in an acute angle to form an open arrowhead.RClosedArrowRClosedArrow (PDF 1.5): a closed arrowhead pointing the other way.ROpenArrowROpenArrow (PDF 1.5): an open arrowhead pointing the other way.SlashSlash (PDF 1.6): a short line at the endpoint, 30 degrees clockwise from perpendicular to the line.SquareSquare: a square filled with the interior colour.