Homemade glass cutter tool using old spark plug

NGK Spark Plugs ??? Do Not Throw Old Spark Plugs in the Trash !
https://www.youtube.com/watch?v=4VKf7gi8rL4

As a child back in the 60's, we learnt that the ceramic part of a spark plug would break a car window if thrown at it hard enough.

Thanks Mr.DK DIY! We've added your Glass Cutter to our Miscellaneous category,
as well as to your builder page: Mr.DK DIY's Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="https://www.homemadetools.net/homemade-glass-cutter"> <img src="/uploads/247692/homemade-glass-cutter.jpeg"/> </a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="https://www.homemadetools.net/homemade-glass-cutter">Glass Cutter</a> <span> by <a href="https://www.homemadetools.net/builder/Mr.DK+DIY">Mr.DK DIY</a></span> </div> <div class="tags">tags: <a href='https://www.homemadetools.net/tag/glass'>glass</a>, <a href='https://www.homemadetools.net/tag/cutting-tool'>cutting tool</a> </div> </div> </div> </div>