[Ref. Laszlo Simon in 131011 MMDigest --

You are talking about the Duo-Art note and expression cut-out boxes.
They are simple to make but, the question here is, does your Duo-Art
stack have 80 notes or 88 notes?  The box in the picture would be the
cut-out for the 4 Duo-Art holes in the tracker bar.

If there is one of these boxes pictured on each side (bass and treble)
then they are only for [the hoses connecting to] the expression holes,
and your stack is an 80-note stack and there were never any hoses
attached to the 4 note holes below the Duo-Art tracker bar holes.

If your stack is 88 notes then the box you show will be two-sided and
one side will be Duo-Art holes while the other side will be note holes.

Doug L Bullock
http://thepianoworld.com/