This weekend U.S. seamstresses both professional and amateur sat down in front of their sewing machines with just one pattern on their mind: face masks for healthcare workers battling the COVID-19 outbreak. With hospitals, senior homes, and first responders putting out desperate calls for masks, sewists including Jessy Gillespie, a retiree in Bossier City, La., created groups to field urgent requests, pass them along to other seamstresses, and then distribute the masks where needed.

Handmade masks are far from ideal, but in areas where N95 masks and surgical masks are in short supply, handmade masks are being used to extend the life of medical-grade masks, which would typically be disposed of after seeing a single patient. In some cases, where there's an even greater shortage, homemade masks are being used as a primary form of protection.

While a surgical mask can filter 90% of virus-sized particles, a mask made of, say, an anti-microbial pillowcase filters about 70%.

Gillespie founded her Facebook group "Sew You Care" on Friday. By Sunday the group had distributed more than 1,000 handmade masks around the country. Now, even with more than 1,600 members, the group is struggling to keep up with the need. Gillespie is a longtime organizer for relief efforts, though this is her first time calling on sewing enthusiasts.

“I recently retired from it this year, but I was the vice president of Cajun Navy Supply. We specialized in logistics getting humanitarian aid into disaster areas,” Gillespie told Fortune.

She said she originally promised her husband she wouldn’t get involved, but then she saw the need for masks and a way to help.

“I usually do hurricanes and stuff like that,” Gillespie said. "What's really cool about this is that we can just mail them, so we can have people working all over, from grandmothers to stay-at-home moms to cosplayers. Everybody that has a little bit of extra fabric is jumping in on this and it's awesome.”

She decided to create the group after talking to friends that are doctors and nurses that said they had limited, or in some cases, no personal protective equipment (also known as PPE).

“I started seeing articles being shared that are saying these nurses are wearing bandanas, they’re wearing handkerchief’s tied across their faces,” she said. “It became a very scary realization.”

So far, President Trump has said that he will not compel companies to make masks, although some, including Hanes, have said they plan to.

Gillespie’s group is using a pattern for masks provided by the CDC. She’s organizing requests and the distribution of the masks through Google forms. Requests for masks are vetted by a team member, and then those requests are matched with a seamstress in the area where those masks are needed so they can be distributed quickly.

“What caught me really off guard is how badly they’re actually needed,” Gillespie said. “We're looking for more seamstresses. Currently, we're trying to root them out of everywhere that we can find them.”

While Gillespie’s group of seamstresses is one of the largest, it’s definitely not the only one.

Running low on masks, Deaconess Hospital in Evansville, Ind. put out a request last Wednesday asking for the community to sew masks. Thanks to an overwhelming amount of support, by Friday it was able to meet its demand and launch a directory to connect other groups that need masks with people that can potentially donate them.

As of Monday, the list of hospitals, medical facilities, and first responders that need masks was 2000 places long.

That need may be due, at least in part, to a lack of available materials. For instance, Wazoodle Fabrics in Pennsylvania, which makes medical-grade fabric for masks, was originally ordered to close because it was deemed a “non-essential” business. The manufacturer was later allowed to reopen and is now sold out of many of its fabrics and, for now, had to stop accepting new ones.

In Washington, an upholstery business, Kass Tailored, has been making masksfor local medical workers.

The lack of masks is a problem that's getting worse around the country, but it's also one that's bringing people together as well.

"The coolest thing to me is that you're seeing so many posts of grandmothers sitting down with their 12-year-old granddaughters and teaching them how to sew. This art form that we all love so much is making a huge comeback in a really crazy time," Gillespie said. She compares the work to being a modern-day Rosie the Riveter, "except with sewing machines and flannel."