Understanding the type of knots that are allowed to be opened on Shabbos.
Understanding the Difference Between Three Melachas: 1-ZOREH, 2-BORER, 3-MERAKED;
מבטל כלי מהיכנו (nullifying a vessel from its normal usage). Putting a כלי (utensil/vessel) under candles to catch oil, to catch the candle and...
The Separation Has to Be with אוכל and פסולת (Good and Bad);