Keilim, Chapter 16, Mishnah 2. This chapter is occupied with a single question asked about one type of vessel after another: at what stage of its manufacture does an object stop being raw material in the craftsman's hands and start being a real keli, a utensil that can receive tumah? Our mishnah applies that question to woven baskets.
To follow the mishnah, it helps to picture how such a basket is put together. The weaver gathers twigs and lays them out radiating from a center point, so that the arrangement looks something like a star. He laces them together, forming a small circle in the middle, and keeps working outward in widening rings until the flat base is as broad as he wants it. Then he bends the ends of the twigs upward and continues weaving, and the walls of the basket rise. The question is at which point along this process the object crosses the line into becoming a usable vessel.
Baskets of stiff twigs
The mishnah begins: "hasalim shel etz, misheyachsom viyekanev", baskets made of wood, meaning of stiff twigs laced together, become susceptible to tumah once the craftsman has finished off the rim and performed the kinuv, the trimming. Two finishing operations are named. First he closes and binds the upper edge, the rim of the basket. Second he snips away the twig ends that protrude, both on the outside of the basket and on the inside. Only when both have been done is the basket fit for use, and a vessel fit for use is a vessel that can become tamei.
Baskets of palm leaves
A different raw material yields a different ruling. "Veshel temarah": here the weaver has plaited his basket out of date palm fronds rather than rigid twigs. Of such a basket the mishnah rules that tumah can attach to it "af al pi", even in a case, "shelo kinev mibifnim", where he pared the projecting tips flush along the outer surface alone and left the inner face rough. The mishnah supplies its own reason, shekein mekayemin: baskets of this sort are habitually maintained in exactly that condition. Their owners put them straight to work and never go back to smooth out the interior. Since nobody treats that pruning as part of what makes such a basket finished, its absence cannot postpone the object's status. From that point it counts as a keli, and tumah can take hold of it.
The kalkalah
The mishnah turns to a third item: "kalkalah, misheyachsom viyekanev viyigmor et hateluyah". A kalkalah was a basket plaited out of reeds, and its manufacture demands three separate steps before halachah treats it as a vessel. The rim must be closed off and bound; the kinuv must be carried out, meaning that the reed tips left jutting along both faces of the weave, inner and outer, are clipped away; and the teluyah must be completed, that is, the cord by which the basket will be suspended from a wall has to be fastened on. Once that cord is in place the work is over, the object has become a keli, and from then on tumah can attach to it.
Cases for glassware
Two final items round out the mishnah: "beit halegininin uveit hakosot", plaited holders, one shaped to hold small glass flasks and one to hold glass drinking cups. Of these as well the mishnah teaches that tumah attaches "af al pi", even where the artisan, "shelo kinev mibifnim", cut the palm strips flush on the exterior only and left the inner side untouched. The justification repeats what was said of the palm baskets, shekein mekayemin: holders of this kind are kept and handled in precisely that state. People load their glassware into them without ever paring the inner strips, so a rough interior is no shortcoming at all. Such a holder already ranks as a keli, and it is already fit to receive tumah.
The thread running through the whole mishnah is that the halachic moment of completion is set by how people actually use the object, not by how polished a craftsman could theoretically make it. Where the trimming is what makes the basket usable, the basket waits for it. Where common practice is to use the basket as is, the basket is a vessel already.