Assembly Line Interlock and Guidance system was built to synchronize four assembly lines that runs in parallel. In order to assembly multiple variety of products with different kind of materials, the operators have to be guided to avoid mistakes. Complicating the manufacturing process, is the needs of assembling the products in a synchronized period between four assembly lines which outputs supply each other. To answer the challange, we built the system to fulfill the customer`s needs with OMRON`s PLC and LUMEL`s Touch Screen HMI in conjunction with DeviceNet communication system.