Understanding the type of knots that are allowed to be opened on Shabbos.
Gathering Nuts and Candies, etc. at an Aufruf, on Simchas Torah, etc.
Understanding the concept of "שכר שבת בהבלעה" (shabbos earnings included with weekday earnings).
מחמת חסרון כיס Machmas Chesron Kis: Moving a Refrigerator;