Understanding the type of knots that are allowed to be opened on Shabbos.
hanging window shades; Venetian blinds; picture frames on Shabbos.
Vegetables Buried Temporarily in the Soil, Pulling Seeds from Dandelions. Is There Kotzair with Animal Life?;
Eating Hard Food When It Might Make One's Gums Bleed, and Removing Meat Stuck in One's Teeth When Gums Might Bleed;