For Every Bridge, A Troll Traditional Cache

noun: troll; plural noun: trolls

1. (in folklore) an ugly creature depicted as either a giant or a dwarf, often found under a bridge.

verb:

1. make a deliberately offensive or provocative action with the aim of upsetting someone or eliciting an angry response from them, such as hiding a magnetic nano on a bridge.

2. carefully and systematically search an area for something.