amphora noun two handled narrow necked vessel with a pointed base it is commonly buried overnight in the earth with only its neck left above the surface; to cool certain beverages.

It would have been stored overnight, I assumed, in an amphora, buried to the neck in the cool earth. Sometimes Earth girls, first brought to Gor, do not understand why so many of these two-handled, narrow-necked vessels have such a narrow, usually pointed base, for they cannot stand upright on such a base. They have not yet learned that these vessels are not intended to stand upright. Rather they are commonly fitted into a storage hole, buried there to keep their contents cool, the necks above the earth. The pointed base, of course, presses into the soft earth at the bottom of the storage hole. 
Book 21, Mercenaries: pg 257