fish is one solution to this problem). The categories of labors prohibited on Shabbat are exegetically derived – on account of Biblical passages juxtaposing Shabbat observance () to making the Tabernacle () – that they are the kinds of work that were necessary for the construction of the Tabernacle. They are not explicitly listed in the Torah; the Mishnah observes that "the laws of Shabbat ... are like mountains hanging by a hair, for they are little Scripture but many laws". Many rabbinic scholars have pointed out that these labors have in common activity that is "creative", or that exercises control or dominion over one's environment. In addition to the 39 melakhot, additional activities were prohibited by the rabbis for various reasons. The term shomer Shabbat is used for a person (or organization) who adheres to Shabbat laws consistently. The (strict) observance of the Sabbath is often seen as a benchmark for orthodoxy and indeed has legal bearing on the way a Jew is seen by an orthodox religious court regarding their affiliation to Judaism. Specific applications Electricity Orthodox and some Conservative authorities rule that turning electric devices on or off is prohibited as a melakhah; however, authorities are not in agreement about exactly which one(s). One view is that tiny sparks are created in a switch when the circuit is closed, and this would constitute lighting a fire (category 37). If the appliance is purposed for light or heat (such as an incandescent bulb or electric oven), then the lighting or heating elements may be considered as a type of fire that falls under both lighting a fire (category 37) and cooking (i.e., baking, category 11). Turning lights off would be extinguishing a fire (category 36). Another view is that completing an electrical circuit constitutes building (category 35) and turning off the circuit would be demolishing (category 34). Some schools of thought consider the use of electricity to be forbidden only by rabbinic injunction, rather than a melakhah. A common solution to the problem of electricity involves preset timers (Shabbat clocks) for electric appliances, to turn them on and off automatically, with no human intervention on Shabbat itself. Some Conservative authorities reject altogether the arguments for prohibiting the use of electricity. Some Orthodox also hire a "Shabbos goy", a Gentile to perform prohibited tasks (like operating light switches) on Shabbat. Automobiles Orthodox and many Conservative authorities completely prohibit the