The Square Knot, sister and neighbor of Georgetown dive bar the 9 Lb. Hammer, provides American diner food, and it is everything a diner should be: utilitarian, kindhearted, and tidy, with good coffee and breakfasts and hamburgers and an especially great hot turkey sandwich. You should also be aware of the existence of the Square Knot’s porter milkshake, a vanilla shake with chocolate syrup and locally made porter beer.