To build your production line, begin by constructing a splitting manifold that leads into four smelters on a Mk. 2 line, ensuring it can carry 90 Iron Ore per minute. Next, position mergers directly in front of each smelter and connect their outputs in a merger-manifold setup to streamline the iron processing.

Now, arrange five constructors in a line with their inputs and outputs facing the same direction. Set the first three constructors to produce Iron Plates and the last two for Iron Rods. In front of the second Iron Plate constructor, place a merger and connect all Iron Plate constructors to this merger. Repeat this process for the Iron Rods, ensuring they are also connected to a merger.

After that, position three constructors next to the Iron Rod constructors and set them to produce Screws. Behind the center Screw Constructor, place a splitter, and on the opposite side (where the green output arrow is located), install a merger. Connect all Screw Constructors to the recently placed splitter and merger.

Next, set up two assemblers adjacent to the Screw Constructors, leaving space for a in between. On the nearest input to the Screw Constructors, place a splitter directly behind the assembler and connect it with a conveyor belt. Route another conveyor belt to the same input on the second assembler, utilizing Straight Mode for a smooth connection.

To connect the Iron Plates, place a splitter behind the unused input on the assembler farthest from the Screw Constructors. Stack another splitter on top of it, and then delete the lower one for a clean connection. Finally, using Straight Mode, route the connection from the elevated splitter to the second assembler.

Ensure that all inputs and outputs are perfectly aligned for optimal efficiency.