What is "hay barrack"

A hay barrack (haybarrack) is an open structure with a movable roof for storing loose hay on a farm. Hay barracks were widespread in northern Europe in medieval times, also found in the Alps and North America, but are rare today. Early usage of this term was noted as being peculiar to New York state. Hay barracks were used in much of Europe and parts of colonial America, but were very common in the Netherlands, where they are called hooiberg or kapberg.