Understanding the constructive and destructive part of it (mochaik).
Ear Plugs, Examples of Strengthening an Item on Shabbos, Hairspray, Stretching Shoes, etc.
Understanding the Concept of גרמא. What Should One Do If a Candle Fell on the Tablecloth and Caught Fire?;
Various Examples of Sifting and Straining: When Meraked May Be a Rabbinical Prohibition;