The triple robe is described in the Vinaya with the exactness of a legal text, because that is what the Vinaya is. The antarvasa is worn at the waist and reaches below the knees. The uttarasanga covers the upper body and is the robe worn for going into a village. The samghati is a doubled outer robe, warmer, used for formal occasions and as a covering at night.
The pattern is attributed to a specific request. The Buddha, looking at the cultivated land of Magadha, is said to have asked Ananda whether he could make robes on that model, and Ananda produced the arrangement of rectangular panels separated by borders that all subsequent robes follow. The number of panels varies, five, seven, nine and upward, and in several traditions the count corresponds to the formality of the garment.
The cutting matters as much as the pattern. Whole cloth is deliberately cut into strips and sewn back together, which destroys its commercial value, discourages theft and removes the possibility of a fine garment. A robe is therefore made worse before it is made.
To the three robes the tradition adds five more items to make the eight requisites: an alms bowl, a razor, a needle, a belt, and a water strainer, the last so that the monastic does not kill small creatures by drinking. Theravada practice adds a bathing cloth and other permitted items, and the counts differ by school, which is why the number of pieces in the set is stated differently in different places.
The kathina, offered by the laity at the close of the rains retreat, is the one occasion in the year on which a community formally receives cloth, and it carries specific relaxations of the robe rules for the months following.