"There he saw a well in the open country, with three flocks of sheep lying near it because the flocks were watered from that well. The stone over the mouth of the well was large. When all the flocks were gathered there, the shepherds would roll the stone away from the well's mouth and water the sheep. Then they would return the stone to its place over the mouth of the well." NIV translation
As Jacob arrived in the area of Haran, he saw a well that was used to water the sheep that were pastured in the area. The mouth of the well was protected by a large stone so that the well could not get contaminated as when an animal fell in and died. That well was a matter of life and death for the flocks as well as the shepherds of the area. It is also a picture of the Word of God as well as the Spirit of God in the life of a believer.
Just as the water was vital to sustain them, the Word of God, as delivered through the Holy Spirit, is what sustains us as Christians. We are reminded of Jesus' words when He was faced with the temptation from the devil to turn the stone to bread. His answer was that we are sustained from the words that flow from the mouth of God (see Matthew 4:4).
The shepherds removing the stone is a picture of the work of Jesus Christ on the cross as He died to give us total access to the sustenance (water) of God.
The fact that the shepherds would put the stone back over the well after they watered their flocks is a reminder to us that the Word and Spirit of God cannot be taken for granted. Through His death on the cross, Jesus rolled the stone away from the well so that everyone (including those who are not a part of the flock) could have access to God. But, as with the shepherds closing up the well, there is a day coming in which that access will be restricted to those that are a part of the flock of God. This time is commonly called the Judgement Day and it is closer now than ever before.