How long does a knot have to be tied to be considered a "קשר של קימא". (Knot of permanence).
Wages on Shabbat - Introduction to what it is all about.
Folding garments that don't have a recognizable crease, folding so that it fits in the drawer or closet, and cleaning off the table after...
Using an Intercom, Recorder, or Microphone on Shabbos;