  We consider double plumbings of two disk bundles over spheres. We calculate
the Heegaard-Floer homology with its absolute grading of the boundary of such a
plumbing. Given a closed smooth 4-manifold $X$ and a suitable pair of classes
in $H_{2}(X)$, we investigate when this pair of classes may be represented by a
configuration of surfaces in $X$ whose regular neighbourhood is a double
plumbing of disk bundles over spheres. Using similar methods we study single
plumbings of two disk bundles over spheres inside $X$.
