In the continuing discussion of Rabbi Yehuda and the Hakhamim regarding the maximum height of the cross beam – the board that symbolically closes the open end of a Mavoy – the Gemara quotes a which states that the cross beam can be placed more than 20 amot (=cubits) from the floor if the cross beam is decorated in a way that makes it stand out in an obvious way, thus fulfilling its purpose as a “heker” (a reminder). The suggestion stems from the fact that such a decoration – called an “Amaltera” (cornice) – appeared over the doorway in the Temple, which, according to our Gemara, is the model for the rules of the Mavoy (an alleyway that is surrounded by courtyards on three sides, with the fourth side open to the public domain).
Two opinions are brought by the Gemara to define what the “Amaltera” looked like. Rav Hama says that it was decorative wood carvings in the shape of birds’ nests (“Kinei”), while Rav Dimi reported that in Israel the tradition was that they were cedar poles (“Paskei D’Arza”). Some commentaries explain that the birds’ nests were small, decorative openings made in the side of the wall, underneath the cross beam, where occasionally birds would nest. According to the Aruk, the boards of cedar wood jutted out from the walls at the edges underneath the cross beam, with each board set a little bit deeper into the wall. This descending pattern created an optical illusion that the cross beam was closer to the ground than it really was.
With regard to the height that has been discussed – 20 amot – the Gemara presents a difference of opinion about how an “ama” is defined. It is important to understand that, before measurements were standardized, they were based on the approximate length of a handbreadth (tefah) or an arms-length (ama), so there were bound to be variations in the measurements.
According to Abayye, some dimensions in Jewish law are measured with an ama that is five tefahim long, while others are measured with a six-tefah ama. Rava, on the other hand, maintains that all measures use the six-tefah ama. The varying length of the “ama” stems from whether the fingers are held together loosely – “sohakot” (smiling) – or held close together – “atzeivot” (sad). The Aruk explains that the longer “ama” is made up of tefahim where the fingers are held loosely, like a man whose lips are spread far apart. The shorter “ama,” comprised of tefahim with the fingers held tightly together, is similar to a sad person who purses his lips tightly together.