With an exterior lit only by a neon window sign reading “cocktails,” it’s easy to assume from the outside that Club Charles is your standard dive.

Neon signs were enough of a novelty that when the Las Vegas Club on Fremont Street erected one in 1930 it made the Review-Journal’s front page.

As anyone who’s taken a trip to Li Po lounge or 500 Club can attest, neon signs still have a foothold in San Francisco. But they’re relegated to mom-and-pops, small businesses and the like.

Inside The Neon Company studio on DeKalb Avenue, a guild of craftspeople spends their days hand-fabricating neon signs in much the same way their progenitors did a century ago. The company, which ...