Understanding the type of knots that are allowed to be opened on Shabbos.
Vegetables Buried Temporarily in the Soil, Pulling Seeds from Dandelions. Is There Kotzair with Animal Life?;
Sucking out juices from orange pieces, grapefruit pieces, challah dipped in wine, etc.
putting in and taking out a extra piece of the table; removing rust from a utensil; an adult playing with a child Lego, fixing...