It shouldn’t have come to this, but here we are. The world is running out of face masks for health care workers, which is one reason American officials, including the surgeon general, have warned members of the public against buying their own masks for protection against the coronavirus.

But that doesn’t mean face masks for the public are a bad idea, if we had enough masks. Contrary to what American officials told us, many studies show that widespread mask-wearing might be a very effective complement to hand-washing, social-distancing and other measures to mitigate the pandemic. Health officials in China, Hong Kong, Singapore and Japan suggest that people wear masks in certain situations — if they’re symptomatic, for instance, or if they’re in crowded, not-very-well-ventilated places, like airplanes. Studies have also shown that mask-wearing (in conjunction with hand-washing) reduces the spread of infection within households or other shared living spaces, like residence halls.

But how to get your hands on a mask, when there are no masks? The internet has a plan: Make your own.