WHATS THE DIFFERENCE BETWEEN 4 WAY LOCATOR AND 2 WAY LOCATOR?
4-way mean you prevent movement at 2 axis (+X, -X, +Y and -Y) on the plane. Generally you have cylindrical pin on the fixture and circular hole at workpiece part.
2-way mean you prevent movement only at 1 axis on the plane. And generally you have cylindrical pin on the fixture and slot hole at workpiece part.
We use generally one 4-way and one 2-way at the same time. We need freedom of movement. Because the distance between pins at the fixture or the holes at the workpiece might not fully accurate.