Fingerprints; invisible ink; writing on one skin; x-rays.
introduction to various types of knots;
Inserting Stuffing into a Couch Pillow, Detaching Connected Toothpicks, and Putting Back an Unattached Chair Seat or Cushion;
Is one allowed to hang up pants not on the crease, folding towels and undergarments, and hanging up dry clothing on Shabbos;