Filling a roundish hole in a plank is a not-uncommon requirement: knot holes, or reclaimed wood accompanied by cuts for plumbing and heating, can present boards that need something beyond wood filler ...
Sometimes a hack doesn’t need to be rocket science to be useful. Take for instance [MofigoDIY] using an old spark plug to build a glass cutter. Sure, going to grab a glass cutter at the hardware store ...