Figure 1. A Class-Responsibility-collaborator (CRC) index card
All the information for an object is written on a 4" X 6" index card.
These have the advantage that they are cheap, portable, readily available, and familiar.
The class name appears underlined in the upper-left hand corner.
A bullet-list of responsibilities appears under it in the left two-thirds of the card.
And the list of collaborators appears in the right third.