i play archtop guitars on a strap even when sitting, i like to keep 'em high – and this vintage Framus Sorella was indeed old, precious and delicate... and never had a strap button!
i didn't want to drill a hole in its side, and i didn't want the weight of the instrument to hang off the neck (as we used to play dreadnoughts, when we were young).
the Daddario DGS15 turned out to be quite the pretty and useful solution.
I wrapped the longer bit around the end of neck, sliding it between the fretboard's underside and the guitar's top, ending up with the (female) clip on the side, close to the neck heel, where a strap button would be usually installed.
the (female) clip is firmly kept in place by its cord, just its tension across neck's heel and top, and stays with the guitar all the time, in its case, too.
the (male) clip is looped across the strap's eyelet, slipped inside the case pocket for safety during transport.
when you pull the guitar out of the case, you simply have to plug the clips together, and you're good to go – no parts loose in the case, no parts that can get lost or forgotten at the gig, and no holes drilled onto an old instrument... at a very affodable price, after a 5' experiment to set the right tension once for good, set and forget.