Andrew adds some stability to the Billy bookcases.
“My wife and I just purchased 6 Billy bookcases to go in our dining room. Having read some people complain that they could be a bit wobbly, I did the following. When assembling, I put glue in all the dowel holes connecting the top/bottom/middle shelf to the case sides, and then when installing, I connected them together into 2 groups of 3 to make a rigid structure, that’s attached to the wall.”
See the process photos on Flickr.