Within feature geometry, different claims have been made about the range, unity and location of manner features with little support for a Manner node as a unit of subsegmental structure. The issue is reconsidered, drawing on evidence of interacting error patterns in the developing systems of three young children acquiring English. The results reveal that obstruent stops and glides can serve as targets of assimilation when the triggering features are [continuant], [nasal], or [approximant], but also block as targets under superficially similar circumstances. It is argued that these three features are dependents of the same node, namely Manner, and that default features must be permitted to be both specified and underspecified underlyingly.