In the Heart of Darkness, it is very easy to forget what is real and what is civilized. The rivets that Marlow talks about, to fix his boat, are very symbolic of his need to become riveted to reality. Marlow feels that he is slipping into savagery from what he sees around him. In the story, The Heart of Darkness, by Joseph Conrad, there is a fine line between civilization and savagery and Marlow needs the rivets to help him find himself in his own soul or where his own reality is. The ivory is another object that causes savagery. The people are trying to find this ivory, but they are only getting themselves deeper into the Heart of Darkness, deeper into savagery, and farther away from civilization.
Marlow is in the Hear of Darkness. Nothing in it is civilized. It is only natural for a person to start turning towards savagery if he or she is surrounded by it. This is why Marlow speaks about the rivets. He says, "What I really wanted was rivets, by heaven! Rivets. To get on with the work-to stop the hole. Rivets I wanted." He doesn't actually want rivets for his boat. He wants rivets for his life to maybe salvage whatever sanity he has left. The nightmares and the things he sees are making him lose touch with reality.
Mr. Kurtz is a perfect example of losing touch with reality. He is insane from being in the Heart of Darkness. He is a very intelligent man, a "universal genius." He is just no longer civilized. Marlow says, "and rivets were what really Mr. Kurtz wanted, if he had only known it." If Mr. Kurtz had the rivets, he would have been able to leave the Heart of Darkness and escape from the savagery and insanity, which had taken over him later in the story.
The ivory also causes savagery. Ivory symbolizes the only sanity that is in all the darkness. It causes people to kill animals and people just so they can have a sense of reality, but all it does is make them more savage. "The only real feeling was a desire to get appointed to a trading post where ivory was to be had." Marlow has a desire to have some light in the middle of darkness. He has a desire for civilization.
As one can see, the rivets and the ivory both cause savagery and insanity. These objects determine what side of that fine line Marlow stands in.