The glue that holds us together? That would be glue.

(click ad) Comical, somewhat disturbing ad for Pattex long lasting glue, via Imelda Ogilvy in Ljubljana, Slovenia (where, during our last e-visit, we saw the biggest soapiest billboard breasts ever [nsfw]). A less cynical interpretation of this visual would be that it's just a cute metaphor; they've stuck with each other through thick and thin. But, judging by the disparate facial expressions, I think we have to assume that these two lovebirds are actually glued to each other (image via).
Previous Pattex glue ads:
Semen-like Elvis & Marilyn sculptures.
Rock & Rollers thwarted from trashing hotel room.