Mechatech - Cutting to Size
The melachah of mechatech is defined by the Rambam203 as cutting [or chopping or breaking or tearing] an item to a specific size, with the intention of using the item according to that specific size or shape. This could be accomplished in one of three ways:
Cutting an item to a specific measurement, measured in amos, inches or centimeters, etc. For example, one has a need for a piece of wood 6 inches long, but the board in his possession is twice that long. In order to cut it down to the appropriate size, he must measure 6 inches, mark a dotted line in the exact place he is planning to cut (thus transgressing the melachah of mesartet) and then cutting it on the dotted line. The cutting on the dotted line is mechatech, since he is cutting the wood to a specific size with the intention of using the wood according to that size204.
Cutting out a specified, smaller area from a bigger area, such as cutting a picture out of a newspaper. Although it is not being cut down to a specific measurement of inches or centimeters, it is still considered cutting it down to size since he is meticulous to cut only the area which contains the picture, to the exclusion of all else205.
Cutting down an item to shape it, such a shortening its length, narrowing its width or sharpening its head, in order that it fits a specific need. Taking a thick piece of wood, for example, and chipping away to narrow it and shape it into a toothpick or to pick a lock, is a form of mechatech, since he is cutting down the wood to be a certain size which will fit the space between his teeth or be able to pick the locked door206. Similarly, narrowing and shaping a candle so that it would fit into a candlestick holder, would constitute a violation of mechatech.
Mechatech applies to all types of material, including soft, delicate material such as paper, nylon and clothes, or hard material such as wood, metal or stones. It does not apply to perishables such as human or animal food or medications. While mechatech min ha-Torah is usually performed with an implement of some sort, such as a knife or a saw, it can also be done by hand if this particular item is usually cut or torn by hand, e.g. a piece of paper207. Mechatech does not apply to trees or plants or anything which is attached to the ground208.
As stated earlier, mechatech only applies to when the item is cut to a specific size with the intention of using that item according to that size or shape. There is, however, a fundamental disagreement among contemporary poskim as to the practical definition of that criteria. Some poskim maintain that whenever an item is cut or torn in a specific area which is marked by a dotted or perforated line it is considered mechatech. For instance, tearing toilet paper on Shabbos is forbidden209 because of the melachah of kore’a, Constructive Tearing. Per this opinion, tearing toilet paper specifically on the perforated line is a violation of mechatech as well, since the person doing the cutting is not tearing randomly, but rather aiming to cut the paper in an exact, specific area which has been previously designated for cutting. In practical terms, therefore, in a situation of kavod haberiyos, maintaining human dignity, where it is permitted to tear toilet paper with a shinui210, one should avoid cutting it on the perforated line, to circumvent transgressing the additional prohibition of mechatech211.
Other poskim, however, disagree. They hold that mechatech does not apply in this case since cutting the toilet paper on the perforated line is not due to its specific size or shape, but only because it is easier and more convenient to tear it on the precut perforated line. Had the company chosen to make the perforation elsewhere on the paper that would been acceptable as well, which indicates that size and shape do not play a role in the decision as to where to make the cut212.
There are several other practical applications which would depend on the above dispute: [Please note: This discussion covers the melachah of mechatech only. In some of the situations described below, there may be other melachos involved as well.]
Many food packages, including juice or milk bottles, are sealed with a plastic cover and are opened by removing a plastic strip near the top of the package. The strip is pre-marked and sometimes already perforated and is easily removed before the contents of the package or bottle are consumed. Whether mechatech applies in this case will depend on the above dispute, since the strip is being cut in a specific place, but the specified place is not defined by a size or a shape but merely by convenience213.
Opening a twist-off plastic soda bottle cap which perforates along the edge when the bottle is opened might be a violation of mechatech according the first view, since the cap is being cut down in a specific area – along the perforation. But since it is not being cut down to a specific size or shape it is not considered mechatech per the second view214.
Opening a soda can by lifting the tab is also subject to the above debate. The tab is being opened in a specific area and it is already clearly marked and perforated. But the person pulling the tab is not doing so for the sake of the size of the hole or for any other reason, but only because this is an easy, convenient way to open a can. Per the second opinion, mechatech does not apply215.
Tearing a small packet of sugar or sweetener on the marked dotted line is forbidden per the first view216, but is permitted according to the second opinion, as explained above217.
Separating connected leben (or yogurt) cups or freeze pops from each other is a violation of mechatech per the first view, since the separation is being done on the dotted line designated and marked as such. The second opinion maintains that the separation being made at the designated area is not for a specific size or shape but simply for convenience, and is not a violation of mechatech218.
203. Shabbos 11:7. See also Shulchan Aruch ha-Rav 314:16.
204. This form of mechatech is the av melachah, since this was exactly how it was done when they constructed the Mishkan. In order to cover the Mishkan and give it protection, the yerios, made out of ram and tachash skins, needed to be cut down to an exact size. After measuring the size required and marking a dotted line (mesartet), the skins were cut on the dotted line; see Rashi, Shabbos 75b, s.v. v’ayail.
205. Based on Rashi, Shabbos 74b, s.v. mishum mechatech.
206. Rambam, Shabbos 7:11, as explained by Beiur Halachah 322:5, s.v. achad.
207. Mishnah Berurah 322:18. Miderabanan, though, mechatech by hand is forbidden even when a particular item is usually cut with an implement of some sort; see Beiur Halachah 322:5, s.v. echad.
208. Shulchan Aruch ha-Rav 314:16. Other melachos, such as kotzer, will apply.
209. See CHD to Chapter 312 for a discussion whether it is forbidden min ha-Torah or miderabanan.
210. As explained in detail in CHD to Chapter 312.
211. Rav Y.S. Elyashiv (quoted in Orchos Shabbos 11, note 57).
212. Rav S.Z. Auerbach (Shemiras Shabbos K’hilchasah 23, note 62).
213. Rav S.Z. Auerbach (Shemiras Shabbos K’hilchasah 9, note 27 and 33).
214. Rav S.Z. Auerbach (Me’or ha-Shabbos, vol. 2, pg. 550).
215. Rav S.Z. Auerbach (Shemiras Shabbos K’hilchasah 9, note11).
216. Ashrei ha-Ish (mechatech 15)
217. Rav S.Z. Auerbach (Shemiras Shabbos K’hilchasah 9, note 27).
218. Both views are quoted in Orchos Shabbos 11:42 and note 60. [Separating freeze pops from each other, however, may be forbidden because of kore’a according to all views.]