Working in the middle of the night, the team have been documenting their hard work on video sharing site Vine.
Short snaps depict two masked people placing specially created frames around signs in Teddington and Richmond, south west London, and now in central London itself.
People living in Teddington have been hunting the artworks, thought to be a tribute to the work of framers.
In an interview with the Evening Standard, one of the framers said: “Framers are the unsung heroes of the art gallery
“We want to bring attention to the craft of framing and we do that by putting frames around things you wouldn’t normally put them around, in places you wouldn’t normally put them, so people notice the frame more than they would normally.
“It’s got a lot more attention than we thought it would.”
The pair have gained the attention of media, and have appeared on London's evening news.
— Faye Barker (@FayeBarker) September 10, 2015
They've even say they considered attempting to frame the sign on Westminster's Downing Street.
And by working to measure the signs in advance, fitting the frames takes only a few minutes.
But there's just one problem - pesky thieves keep stealing the frames as they're such good quality.
about in #London
it's the art message that has to be heard pic.twitter.com/XK4GHGjJpW— STREETARTDROP (@streetartdrop) September 10, 2015
It's thought the framers are connected to Is It Art? a Teddington shop specialising in high-end picture framing.