Mode of indication is the way an expression directs understanding toward a quality or meaning. It may be direct naming or may operate through simile, metaphor, allusion, or a described condition or action.
Calling a man brave directly names the trait. Comparing him to a lion suggests bravery through another image. Portraying his treatment of visitors may indicate generosity through a particular scene.
The key question is whether the poets merely share the quality described or also share the distinctive sign used to reveal that quality.