The Sechach is the covering of the Sukkah structure that Jewish people live in for the week-long festival of Sukkot.
What materials can Sechach be?
Sechach must be a detached product of the earth. Wood in all it’s varieties may therefore be used- for example bamboo and leafy branches. In the case of a living tree that provides shade for the Sukkah, this is, according to Jewish law, not acceptable.
What about the height of the Sukkah itself?
The maximum height of a Sukkah is twenty amot. An amah (plural amot) is a Biblical unit of measurement that measures between eighteen inches and two feet. Therefore, the maximal height of a Sukkah is between thirty and forty feet. The minimum height is ten tefachim. A tefach (plural tefachim) is another Biblical measurement and it is the size of a fist; between eight and 9.6 cm. The minimal height of a Sukkah is therefore between 32 and 36 inches.
How thick must the Sechach be?
The Sechach must be thick enough to provide more shade than sunlight in the daytime. At nighttime, it must not be thick enough to block the brightest stars.
What is “active” and “passive” Sechach?
There is a principle from the Torah called “Ta’aseh v’lo Min ha’Asuy” which means that certain commandments should be done actively and not passively. This is so regarding Sechach too. Practically this means that the Sechach must be laid intentionally and the passive “arrival” of Sechach is not enough. An example would be the incorrect usage of bundles of hay as Sechach. The use of bundles of hay is forbidden because often hay bundles will be dried on top of structures such as that of a Sukkah and the one drying the hay may decide later on to use the hay as Sechach. Such an instance would be an example of passive placement of Sechach.