I just started using the cradle I built for our second child. I rocked
it a little bit and it started rubbing the wall. I pulled it out and
rocked some more. Soon it was rubbing again.

The crazy thing walks toward one end -- quickly. It covers about 1/8
inch with every rock.

What did I do wrong to cause this? Or should a rough carpenter just not
even try to play furniture maker?

thanks.