Use once as a free action: if your bishop still stands on its home square (c1 for white) and your knight on b1, they swap places.
You draft Flea Market Find in either mode. Free action: you choose when to use it, and it resolves without costing your turn.
As a item card, it is a one-use consumable, drafted in either mode.
“The bishop haggled the knight out of his parking spot.”