One design advantage of my marimbas is their ability to accept a quick swap out of, say an F# bar for the F bar, getting you into the key of G. Or a Bb for the B, getting you into the key of F.
So that thin cording you see snaking over the bars allows them to remain on the instrument no matter how fortissimo they are bonked, whilst allowing, with a simple twist and pull at the end of any bar, removal of said bar. It's worked in thousands of Bourne Marimbas for well over a decade now. Also then, the bars remain on the instrument as it is tilted upright for wheeling and storing.
While many opt for the F# and Bb bars so common in Orff music, I occasionally get a request for OTHER accidentals as well. How about C#s to get you into the key of D. Or whatever keys or modes are represented in THIS array:
|name that key|
One advantage to being a one-person operation: I can create whatever scale you are dreaming of!