What does Genesis 31:45 mean?

Laban has suggested a covenant between himself and Jacob. They have aired their differences, including Jacob's extensive abuse at the hands of Laban's greedy manipulations. Laban, for his part, sees all of Jacob's wealth as his own, since Jacob was his servant, and refuses to accept the fact that his daughters are leaving him voluntarily. However, thanks to a warning from God (Genesis 31:24), Laban is not willing to use force to stop Jacob from leaving.

After all of this, the two men have come to an agreement to simply part ways. Jacob agrees to this contract and uses a stone to set up a pillar to mark this pact. This pillar is similar to the one Jacob erected from his stone pillow, after the Lord appeared to him in a dream at Bethel (Genesis 28:18). He will set up another pillar after Rachel dies (Genesis 35:14, 20). These pillars mark significant events in Jacob's life.