A line that means one thing.
Draw a line between two boxes and everybody reads a different relationship into it — owns, uses, becomes. UML exists so that the line means one thing, and each of its six relationships is drawn here as the specification draws it.
A use case opens its sequence diagram.
Place an order carries a green dot: under it is a board of its own, where the order is followed message by message — the customer, the app, the order and SoHo's till. The lifeline named Order is the class Order from the classes board, not a copy of it: rename it on either board and both say the new name.
Attributes are fields of the object.
A class keeps its attributes and operations as lists on its object, and the figure's compartments draw them. Redraw Order as a plain rectangle for a five-minute sketch and they are still there; draw it as a class again and the compartments come back.
Every figure, named.
The toolbar's own names — what you pick is what this list says: six groups, 59 figures.