<polyline points = "x1,y1 x2,y2 x3,y3 .... xk,yk" />
<svg width="200px" height="200px" viewBox="0 0 100 100">
<use xlink:href="grids.svg#grid_100x100"/>
<!-- parallelogram -->
<polyline points ="5 20, 20 20, 25 10, 35 30, 45 10, 55 30, 65 10, 75 30, 80 20, 95 20"
style="fill:none; stroke:rgba(44,95,45,1); stroke-width:2"/>
</svg>
Avoid filling polylines
<svg width="200px" height="200px" viewBox="0 0 100 100">
<use xlink:href="grids.svg#grid_100x100"/>
<!-- polygon with intersecting lines -->
<polygon points ="5 20, 20 20, 25 10, 35 30, 45 10, 55 30, 65 10, 75 30, 80 20, 95 20"
style="fill:rgba(44,95,45,0.3); stroke:rgba(44,95,45,1); stroke-width:2"/>
</svg>