For strict adherents of Judaism, Saturdays can be tough days. On Shabbat, whish lasts from sundown each Friday to sundown on Saturday, Jewish law (Halacha) prohibits melakha, which loosely translates to "work;" in practice it means one cannot push an elevator button, turn an appliance on or off, or open a bottle of soda, as some examples.

The laws are pretty specific; for instance, you can open a refrigerator, but if the light inside the 'fridge visibly illuminates, you've broken Halacha. As a workaround, some Jews will disconnect the bulb prior to Shabbat; others will cover the bulb in black tape. There are also interpersonal workarounds: You can ask a non-Jewish person to turn an air conditioner on for you, for instance.

Because some of these workarounds are inconvenient, a company called Kosher Innovations sells an entire line of products that are rabbi-approved and allow you to perform certain tasks without technically violating Halacha. Some examples:

The KosherLamp Max

"A simple twist reveals or hides the light on this innovative reading lamp - and it can be used on Shabbos according to halacha!"

The Kosher Fridz-eez

"Do you like having a light in your refrigerator all week but need a way to keep the light off during Shabbos or Yom Tov?

"That is what the Kosher Fridg-eez is for. It's designed to hold down the fridge light switch in order to keep the light turned off. When Shabbos or Yom Tov is over, simply pull the plastic tab to remove it, letting the fridge light shine again."

The Shabbos Bottle Opener

"Did you forget to open your soda bottles before Shabbos? Not to worry--the Shabbos Bottle Opener can be used to open plastic soda bottles on Shabbos! It allows you to remove the plastic cap including the plastic ring, without tearing it.

"Normally, the action of unscrewing the bottle cap causes the perforated ring to tear. This is fine for during the week but on Shabbos/Yom Tov, falls under the category of the melacha of Makeh B'Patish (Act of Completion). By separating the ring from the cap, it finishes the cap, allowing it to be removed from the bottle.

"The Shabbos Bottle Opener grips the bottle cap and removes both the cap and the perforated plastic ring at the same time, without tearing the ring. Thus it avoids the melacha of Makeh B'Patish. In fact, one can still replace the cap with the perforated ring still attached, back onto the bottle. One would just need to use the Shabbos Bottle Opener a second time to remove it again."

I find this category of product design completely fascinating. You can check out more of these here.