sheaves, which were laid in oriented sequence. With the advent of large bales since the 1960s, today hay is often stored outdoors because the outer surface of the large bale performs the weather-shedding function. The large bales can also be stacked, which allows a given degree of exposed surface area to count for a larger volume of protected interior hay. Plastic tarpaulins are sometimes used to shed the rain, with the goal of reduced hay wastage, but the cost of the tarpaulins must be weighed against the cost of the hay spoilage percentage difference; it may not be worth the cost, or the plastic's environmental footprint. After World War II, British farmers found that the demand outstripped supply for skilled farm laborers experienced in the thatching of haystacks. This no doubt contributed to the pressure for baling in large bales to increasingly replace stacking, which was happening anyway as haymaking technology (like other farm technology) continued toward extensive mechanization with one-person operation of many tasks. Today tons of hay can be cut, conditioned, dried, raked, and baled by one person, as long as the right equipment is at hand (although that equipment is expensive). These tons of hay can also be moved by one person, again with the right (expensive) equipment, as loaders with long spikes run by hydraulic circuits pick up each large bale and move it to its feeding location. A fence may be built to enclose a haystack and prevent roaming animals from eating it, or animals may feed directly from a field-constructed stack as part of their winter feeding. Haystacks are also sometimes called haycocks; among some users this term refers more specifically to small piles of cut-and-gathered hay awaiting stacking into larger stacks. The words (haystack, haycock) are usually styled as solid compounds, but not always. Haystacks are also sometimes called stooks, shocks, or ricks. Loose Loose stacks are built to prevent the accumulation of moisture and promote drying or curing. In some places, this is accomplished by constructing stacks with a conical or ridged top. The exterior may look gray on the surface after weathering, but the inner hay retains traces of its fresh-cut aroma and maintains a faded green tint. They can be covered with thatch, or kept within a protective structure. One such structure is a moveable roof supported by four posts, historically called a Dutch roof, hay barrack, or hay cap.