This excerpt appears courtesy of Guitar Aficionado magazine. You can read the full article on their website here
As the Sixties drew to a close, guitar manufacturers were faced with a dwindling supply of lightweight ash. This affected Fender in particular, as the company had traditionally relied on this timber for the bodies of its Telecaster guitars. Early attempts to produce a weight-relieved Telecaster using heavier ash yielded a small number of guitars with hollowed-out portions under their pickguards. (These “smuggler’s Teles,” as they’ve become known, are sought after by vintage collectors.) Ultimately, Fender deemed that a more radical redesign would be required.The job fell to famed German luthier Roger Rossmeisl. A specialist in archtop and acoustic designs, Rossmeisl had just defected from Rickenbacker. He conceived of an elegant solution: a “Thinline” model that retained the classic Telecaster body shape but featured a solid center block and hollowed-out upper and lower portions. To accomplish this, wood was removed from the back of the guitar, which was then covered with a thin ash cap.Click here to read the full article.