Have you ever had trouble making the display order of objects stay the way you want? Sadly the DRAWORDER command isn’t always as reliable as I would like it to be. Here is how I force the draw order to stick:
Select the object(s) you want to appear on top, then type the COPYBASE command and hit enter. When prompted for a base point, type 0,0,0 and hit enter. Before you do anything else run the ERASE command (or hit the DELETE key) to erase the selected objects. Then use the PASTECLIP command to paste the objects back into the drawing using 0,0,0 as the insertion point.
This works with XREFs too. If you want one XREF on top of another, simply copy it, delete and paste it back into place. The state of the layers will also stay intact, which is really nice!
When dealing with hatch patterns, there is a dedicated command for that.
I hope this helps!