How is a pin notated?

• A. A small square attached to the boundary on the outside of an action
• B. A small circle inside the action boundary
• C. A diamond shape at the boundary
• D. A rectangle outside the action

Answer: (A)

Pins are shown as a small square placed on the outside edge of an action’s boundary. This outside placement keeps the pin visually separate from the content inside the action and from other notation shapes that mark different concepts. The square shape itself is the standard symbol for a pin, distinguishing it from a circle (which would indicate something else inside the boundary), a diamond (often a decision point), or a rectangle (not used to denote a pin). So when you see a small square attached to the boundary on the outside, that’s the pin notation.