Joint Unit (Unidad-Yunta), belonging to the series of the same name, integrates two separate volumes arranged facing one another. The front faces of these volumes create profiles that complement each other when they come together, both bodies joining together and uniting. This represents mutual communication. Although in this case, the concept of unity is more symbolic than reality. Both parts are anchored to the base, preventing them from coming together. Serrano applies a different finish to the materials which must be interpreted within the meaning of the series. It is the faces, which confront each other and where communication arises, where the artist reserves the most delicate treatment of the piece with burnished bronze. This leaves the exterior part with a rugged finish and dark patina which contrasts with the reflectiveness of the interior face. As stated by the artist: "People who communicate, live together, shapes which adapt to one another, nuclei which together form a bright 'polished' contact unit, nuclei with shapes united through these interior spaces which adjust, squeeze into one another, which can integrate into communities or which can be individuals."