This is an example of an end marker specified with a minimal number of parameters. Note that the stroke color of the original element is not inherited by the marker.
<svg width="800px" height="600px">
<defs>
<marker id="examplemarker"
viewBox="0 0 10 10"
refX="0" refY="5"
orient="auto">
<path d="M 0 0 L 10 5 L 0 10 z" />
</marker>
</defs>
<line x1="20" y1="20" x2="300" y2="300" stroke-width="8" stroke="blue" marker-end="url(#examplemarker)" />
</svg>