Fixing one unit on top of aother

[chris50]

Hello,
I need to fix one wooden bookcase on top of another, but without going through the shelves & was wonder about the best way to do so?
I was thinking of something like a metal rod that run from the top of each side of the bottom bookcase into the bottom of each side of the top bookcase (hope this makes sense). Each unit is 23Kgs & will be supporting approx 75kgs of goods. I guess I could use dowels but wasn't sure if it would be strong enough.
Any suggestions would be most appreicated.
Thanks, Chris

[thedoctor]

Metal dowels should do the trick Chris, if you can get them lined up exaclty. I'd have a practice on some timber off cuts first.

[chris50]

Many thanks for the advice.