Eruvin 3: Someone Will Take Care of It, Right?

Terminology: Amaltra - cornice. Amah - cubit. The implication of having amaltrot, even as high as 20 amot, in your alleyway (in contrast to a sukkah). The subjectivity of the measurements (how many tefachim in an amah, without expressed concern for whose tefach, but a concern for expanded vs. contracted amot). The implication of a larger amah in the context of kilayim (hybrid growth). Also, the implication of a minimum amount for a space to be considered an alleyway. Plus: kila'ei ha-kerem, the distance of seeds from the vineyard, and how to plant without this problem. And: How shared responsibility can mean nothing gets done.