what are these for (see the crummy pics):
... those ought to be around the rear quarter, interior. I took the plastic plug out, and the threads are 1.25 pitch, about 10mm OD, about 15mm depth (off the top of my head). note - if my sig lacks it -this is a late MY, being '87.
I've looked into other questions centered on these ... let's call them holes .... and I already have an idea, but I am trying to keep this thread real simple. if you *know* what these are for, it'd be helpful to know how you know. speculation might be nice, but can easily blow up into a mess.
... what would be very helpful is to know the model year of any users' cars, and any such features in the vicinity of that hole.