Lute (from Latin Lutum, meaning mud, clay etc.) was a substance used to seal and affix apparatus employed in chemistry and alchemy, and to protect component vessels against heat damage by fire; it was also used to line furnaces.  Lutation was thus the act of "cementing vessels with lute".
In pottery, luting is a technique for joining pieces of unfired leather-hard clay together, using a wet clay slip or slurry as adhesive.  The complete object is then fired.  Large objects are often built up in this way, for example the figures of the Terracotta Army in ancient China. The edges being joined might be scored or cross-hatched to promote adhesion, but clay and water are the only materials used.