заводом

In a sentence

• Мы прошли мимо завода по дороге домой.

  We walked past the factory on our way home.

  Here, 'завода' is the genitive case form of 'завод', showing possession or relation in terms of movement related to it.

• Этот мост был построен заводом.

  This bridge was built by the factory.

  Here, 'заводом' is the instrumental case of 'завод', indicating the agent by which the action was performed.

• Он работал заводом в этом городе.

  He worked at the factory in this city.

  Here, 'заводом' might be used contextually to refer to the factory in an unusual literary manner, aligning with the instrumental case, though the standard phrasing would differ.