Prepositions of Agency is a word that indicates some relationship of a noun or pronoun in the context of some agency.

Prepositions of Agency include by, with, with the help of, with the assistance of, etc.

Examples:

1. The soldier killed the enemy with a gun.
2. This page was torn off the book by a small child.
3. We could climb the high mountain with the help of a rope and iron pegs