Fingerprints; invisible ink; writing on one skin; x-rays.
various different ways to work with the BOTTLE CAP attached to the ring on Shabbos;
to clog a small crack in a pipe. Turning off gas range. Putting on, taking off smoke detector. Unscrewing the bulb that's off;
Understanding the Difference Between the Melacha of Kotzair-קוֹצֵר (Reaping) and Gozez-גּוֹזֵז (Shearing);