Conveyor Merger

A Conveyor Merger is a building that takes items from three input belts in sequence and outputs all items onto a fourth belt. If any input is missing the merger takes the items from remaining input belts. If the output belt is slower than the total speed of all input belts, the input items have to wait.

Building
The ' and ' have fairly large collision boxes which are likely to obstruct additional parallel belts. For example, a splitter for belt is likely to block the construction of  belt. It is advised to build other nearby belts before building the splitter/merger.

You can stack the mergers on top of each other, each stacking offset by 2 meter height.

Trivia

 * It is easy to differentiate between input slot and output slot by looking at the shape of LED light at the belt connector. The output is indicated by a arrow-like light, while the input is 3 smaller dotted light.
 * Planning ahead, get into a habit of adding a Conveyor Merger on the output of your production buildings. This allows you to expand that line of production buildings later on.