In the attached file, I would like to make the yellow boundary fit snugly inside the green boundary. Very much like it is now, but now it is just "floating", where as I'd like it to be "attached". How would I go about this?

Once this yellow outline is snapped inside the green square (and same with the red outline), then I would like to change the remaining space between the red and the yellow to a different color. Would I use the "fill bounded areas" tool for this? Or somehow duplicate the curved part of one of the yellow/red outlines?

Thanks,

David

Snapping is used only to position things precisely. So we could probably figure a way to use snapping for this, but the objects would still not be permanently attached. If you want to move them around together, you'll still have to select both, or Group them. You may have already known that, but I'm not sure from the way you worded it.

Unless there's some reason why you can't do this, I think I would convert the yellow, green and red strokes to paths. Then you could Enable snapping, Snap nodes or handles, and Snap to cusp nodes. Engage those 3 buttons, and disengage all the rest. (That's assuming that Stroke to Path results in cusp nodes in the corners of these strokes. Sometimes that command will make sharp corners tightly accute curves, so you may need to do a bit of node editing, after converting to paths.) Then the snapping should work smoothly.

Yes, the best way to change the color between red and yellow lines, is the Fill bounded areas tool (otherwise known as Paint Bucket, or Bucket tool).

There may be other more clever ways to accomplish what you want, but that's how I would approach this problem