"They make the best jeans. Any denim nerd knows that," said Jimmy Fallon before the Rag & Bone show got underway at the former nightclub, Tunnel. Brits David Neville and Marcus Wainwrightco-founder Nathan Bogle left the company earlier this summerdid show cool stovepipe jeans with equally slim seamed blazers to match. And a smart, charcoal gray twill mac had the punk-rock edge they said they were going for backstage. Pinafore dresses in gauze and silk charmeuse, though, are newer territory for the CFDA/Vogue Fashion Fund finalists. It may take another seasonthis is only their third showing women'sbefore the young designers can say that their girlish frocks boast the fit that their other pieces have become known for.