<!DOCTYPE html>
<html>
    <body>
        <p>You should see a line of black pixels at the botton of the gray square.</p>
        <svg width="800px" height="800px" xmlns="http://www.w3.org/2000/svg">
            <defs>
                <clipPath id="clip-out-middle">
                  <rect x="10" y="240" width="200" height="4" />
                </clipPath>
            </defs>
            <rect x="10" y="40" width="201" height="201" fill="black" clip-path="url(#clip-out-middle)"/>
            <rect x="10" y="40" width="200" height="202" fill="none" stroke="gray" />
        </svg>
        </div>
    </body>
</html>