In Ezekiel 37 the word of the Lord came unto Ezekiel, saying:
Moreover, thou son of man, take thee one stick, and write upon it, For Judah, and for the children of Israel his companions: then take another stick, and write upon it, For Joseph, the stick of Ephraim, and for all the house of Israel his companions:And join them one to another into one stick; and they shall become one in thine hand. (Ezekiel 37:16-17.)
The "sticks" mentioned here evidently refer to books, since in those days books were written on long scrolls of parchment, which were then rolled on a stick.
The Bible is commonly understood to be the "stick of Judah" referred to by the Lord in his promise to Ezekiel. Latter-day Saints believe the Book of Mormon is part of the "stick of Joseph" mentioned by the Lord. It is possible that a portion of the original stick of Joseph was the brass plates of Laban, and still other portions might be the records of the Nephites as contained on the large and the small plates of Nephi. In this sense, then, our present Book of Mormon would be only an abridgment or condensation of the parts making up the original "stick of Joseph."
Lehi and Laban were both descendants of Joseph who was sold into Egypt. Thus, they had the right to include their writings on the "stick of Joseph."