A short round flask with a very narrow neck, the gutus held liquids -- wine, oil, ointments -- which were to be poured in the smallest quantities, as Varro explains in De Lingua Latina 5.26, a guttis "by the drop."
While the flask is most commonly found in pottery or metal, Martial 's Epigrammata 14.52 describes a certain gutus corneus which was made from the horn of a steer, but could be mistaken for the more precious rhino horn.
Umbricius lists the gutus here among the familiar items that the slaves are preparing in vain for their master's pre-dinner bath at home. In Saturae 11.158, Juvenal praises the country boy who does not frequent the public baths coyly using the flask to cover his nudity with false modesty.
Horace (Sermones 1.6.118) mentions it (cum patera gutus) among the few rustic table items (Campana supellex) to be found in his country home.