"Screws", by Randall Munroe, licensed under Creative Commons Attribution-NonCommercial 2.5 License
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If you encounter a hex bolt, but you only brought screwdrivers, you can try sandwiching the head of the bolt between two parallel screwdriver shafts, squeezing the screwdrivers together with a hand at either end, then twisting. It doesn't work and it's a great way to hurt yourself, but you can try it!