line-join attribute

Type:"round", "miter" or "bevel"
Used By:shape, All block elements
See:border-style line-cap

How to join the corners of any borders drawn in the document. Usually this is just set on a shape element, but it could theoretically be set on any block element.

This causes the sharp corners on a triangle to be drawn as points.

<shape id="triangle" line-join="miter" width="100" height="100">
    <lineto x="100% y="0%"/>
    <lineto x="50% y="100%"/>
    <lineto x="0% y="0%"/>