As more Americans keep loaded guns in their homes, efforts to sell them new kinds of safety locks are getting stuck by policies intended to block ads for firearms online.

Digital marketing giants including Facebook Inc. and Alphabet Inc.’s Google often reject marketing from companies like Zore, the maker of a high-tech, quick-release gun lock, due to policies intended to forbid ads for the firearms themselves, manufacturers of the devices say.

“It really blocked all the ways we wanted to get people,” said Eytan Morgenstern, Zore’s director of communications. “We’re selling to gun owners and they have to understand why it works.”

These companies are getting “swept up in the general prohibition on advertising firearms,” said Chuck Rossi, a former engineering director at Facebook.

“All of them are eligible for ads, but it’s a constant battle to get their ads through,” he said.