How long does a knot have to be tied to be considered a "קשר של קימא". (Knot of permanence).
how to work with covers on tubes on Shabbos;
What are the circumstances needed to consider one's actions "מדידה של מצוה" (measuring for a mitzvah).
Fruits Which Fell Off a Tree on Shabbos or Before Shabbos. Eating One Fruit at a Time;