includes salting hides and curing as separate categories of activity; the Gemara (Tractate Shabbat 75b) amends this to consider them the same activity and to include "tracing lines", also involved in the production of leather, as the thirty-ninth category of activity. This activity extends rabbinically to salting/pickling foods for non-immediate use on the Sabbath. See further: Chayei Adam Shabbos 32–33, Shulkhan Arukh Orach Chayim 321, 327; Chayei Adam Shabbos 33 Smoothing Hebrew: (Memaḥek) Definition: Scraping/sanding a surface to achieve smoothness. This law contains a sub-law (known as a Tolda) called ממרח Memarayach which prohibits the smearing or smoothing of an already pliable substance. See further: Chayei Adam Shabbos 34–35 Scoring Hebrew: (Mesartait) Definition: Scoring/drawing a cutting guideline. See further: Jerusalem Talmud, Tractate Shabbat, Chapter "Klall Gadol", p. 52. tirone Measured cutting Hebrew: (Meḥatekh) Definition: Cutting any object to a specific size. See further: Mishneh Torah Shabbat 11:7; Chayei Adam Shabbos 36 The Order of Construction Writing Hebrew: (Kotev) Definition: Writing/forming a meaningful character or design. Rabbinically, even writing with one's weaker hand is forbidden. The rabbis also forbade any commercial activities, which often lead to writing. See further: Mishneh Torah Shabbat 11:9–17, 23:12–19; Shulkhan Arukh Orach Chayim 340; Chayei Adam Shabbos 36 Erasing Hebrew: (Moḥek [al menat lichtov shtei otiyot]) Definition: Cleaning/preparing a surface to render it suitable for writing. Erasing in order to write two or more letters is an example of erasing. See further: Mishneh Torah Shabbat 11:17; Chayei Adam Shabbos 38 Construction Hebrew: (Boneh) Definition: Contributing to the forming of any permanent structure. See further: Mishneh Torah Shabbat 10:12–14 22:25–33; Chayei Adam Shabbos 39–44 Construction can take two forms. First, there was the action of joining the different pieces together, just like in the making of the make the Mishkan. E.g., inserting the handle of an axe into the socket is a derived form of this activity. Another type is to add to an already existing structure called Mosif Al HaBinyan. As such, putting a nail into a wall in order to serve a useful purpose such as hanging a picture, would be adding the nail to the already existing wall structure. Making a protective covering (or a tent) is forbidden, as is setting up a fixed partition. Opening and closing a door is perfectly permitted due to the presence of a hinge. This shows that this is the intended use and falls under a heading of