Some jobs need many hands briefly, rather than one extra worker permanently. Imagine several households restoring storm-damaged fences. They work together at one property this weekend and another next weekend, making concentrated labor available without each household hiring a crew.
The exchange is organized around an obligation to reciprocate. In Andean ayni, labor assistance belongs to continuing community relationships. A one-off work party may assemble the same number of hands, but it need not carry an obligation to return the help later.
Whose turn is next?
The schedule carries a promise: accepting help today means remaining available later. That promise is easier to sustain when participants expect continuing relationships and can discuss differences in what each household can contribute.
Suppose one resident has limited mobility but can arrange materials and transport. Counting only hours of physical labor would obscure a contribution the group needs. Conversely, leaving every obligation undefined can turn the most reliable volunteers into a permanent workforce for everyone else.
The group has to make reciprocity understandable without pretending circumstances are identical. Seasonal work, illness, weather, and different task sizes complicate a neat rotation. The attraction is still substantial: a small group can repeatedly create a working crew larger than any member could normally assemble alone.