Fingerprints; invisible ink; writing on one skin; x-rays.
How to Work with Watches on Shabbos. Part #1;
How to work with folding a TALIS when one takes it off on Yom Tov which falls out Erev Shabbos and folding a TALIS...
Is One Allowed to Rinse Off the Dishes if They Know They Will Attract Bugs or Start to Smell?;