By the time Homer's audience encounters Odyssey 23, Odysseus has revealed his identity to his son, his servants, and the suitors, the latter of whom he has slaughtered while his wife Penelope was asleep upstairs. When Odysseus reveals himself to his wife, she does not immediately accept this revelation. She wants to test her husband first and she does so by claiming that she has moved his bed. Odysseus reacts with angry astonishment because he himself had built the bed in such a way that only an almost superhuman effort could move the bed. As soon as Odysseus reveals the secret of how he had made the bed, Penelope
ran to Odysseus, flung her arms about his neck, and kissing his face cried: ‘Odysseus, don’t be angry with me, you who in everything were always the most understanding of men. (A.S. Kline translation).
I like to compare Homer's Odyssey to the story of Goldilocks and the Three Bears. Like Goldilocks, Odysseus tries many different foods, many different chairs, and many different beds (Calypso's, Circe's, even beds of leaves). Only on Ithaca, his native land, does he find the bed that is just right, and that is the bed that he shares with his lawful wife Penelope.
A cautious Penelope, sought after by many clever suitors, uses the bed that she and Odysseus shared for so many years to trick Odysseus into proving his identity. The bed, carved from a tree that has its roots in the foundation of the house itself, is immovable, much like Odysseus and Penelope's loyalty to each other. Only Odysseus knows that it can't be moved without destroying it, and so Penelope knows that when she tells him she's had the bed moved, the only man who would be outraged by this confession is her true husband, the one who built the bed himself and kept the secret. Odysseus's anger is confirmation. Thus their marriage bed is not only a staple of the plot, but also a symbol of their enduring relationship, which has been strong enough to survive a separation of more than twenty years.
In Penelope's hands, the bed also helps reveal the qualities that she and Odysseus both share, and which have perhaps made their marriage such an unusually successful one (a rarity among Greek heroes—just look at how relationships worked out for Paris, Heracles, and Achilles). Both husband and wife share a propensity toward cleverness that is particularly unusual in the story. Odysseus is one of the few Greek heroes to epitomize brains over brawn. Even more remarkable is Penelope, whose womanly craftiness is most unusually accompanied by great virtue and purity instead of moral or sexual corruption.
The bed also represents the equality between husband and wife, similarly unusual in Classical literature; Odysseus tests Penelope many times before he is willing to believe that she has remained faithful and not encouraged (or secretly accepted) any of the suitors who plague her. With the bed, Penelope shows herself Odysseus's equal—she won't simply believe he is who he says he is! She wants to test him, too, and will do so before she accepts him.
The bed allows Penelope to determine without a doubt whether the man who claims to be Odysseus is truly Odysseus. She tells her maid to move the bed for Odysseus in order to make it outside her sleeping chambers. Upon this request, Odysseus becomes upset and explains how this can't be done because he specifically built the bed around the olive tree and it cannot be moved. Upon this explanation Penelope then knows this is her true Odysseus.
oddyseus had built that bed himself and he carved a tree as the base, then he basicaly built the whole house around his bed. so in order to move it, it would ruin the bed. so penelope uses this information to see if he really was odysseus because only they knew about the bed