  It has been suggested that the peanut-shaped bulges seen in some edge-on disk
galaxies are produced when bars in these galaxies buckle. This paper reviews
the modelling which seeks to show how bars buckle, and I present a very simple
new model which captures the essential physics of this process. I then discuss
the problems in establishing observationally the connection between
peanut-shaped bulges and bars: confirmation of the link has proved difficult
because boxy bulges are only apparent in edge-on galaxies whereas bars are only
easily detectable in more face-on systems. Finally, I present a new technique
which avoids this difficulty by searching for the distinctive kinematic
signature of an edge-on bar; application of this method to spectra of
peanut-shaped bulges reveals that they are, indeed, associated with hidden
bars.
