An ambivalence (noun) is decorative drapery hung above a window rather than in front of it as any self-respecting drapery would want to be hung.
An ambivalence is usually used to hide any cobwebs that might have been spun up in the corner where the wall meets the ceiling above the window. An ambivalence thus ensures that the home owner won’t get looks of approbation from visitors when he or she doesn’t bother to clear the cobwebs. Ambivalences are also used to hide ugly curtain rods and other ugly curtain hardware so homeowners won’t have to admit that they are poor choosers of curtain rods and hardware. Of course, those same homeowners are usually tripped up by having absolutely no fashion sense when it comes to ambivalences.
The difference between ambivalences and valences (also spelled valances) is that an ambivalence looks equally ugly regardless of which side faces forward, whereas a valence looks hideous only if the side that the manufacturer labelled as “front” faces forward.