In his prophecy, Ezekiel may have used two sticks—or tablets or rods—speaking to a group of people. He could have taken one and written on it "Judah" or "Judah and his posterity." He would have then taken the other and written, "for Joseph, the stick of Ephraim and for all the House of Israel and his companions." And then what does the Lord say? "Ezekiel, I want you to put those two together, and they will be one in your hand."
Prophets in Israel loved to do this sort of thing, to act out certain events. When Jeremiah wanted to prophesy that the children of Israel were going to be taken into captivity, he draped chains and ropes all over his body and walked through the streets of Jerusalem saying, "We are going to be taken captive." It did not make him popular, but it made an impression. Likewise, Abinadi graphically used a "simile curse" in prophesying about King Noah’s demise (Mosiah 12:3). In saying, in effect, to the people, "Just as I am putting these two little sticks together in my hand, something much bigger is going to happen someday when the Lord will bring these two together," Ezekiel dramatically conveys the idea that the gathering will happen because two books—two writings, two staffs of authority—will come back together.
Book of Mormon Central, "Why Is the Book of Mormon ‘Another Testament of Jesus Christ’? (2 Nephi 3:12)," KnoWhy 494 (December 18, 2018).