How do i make obstacles moving infinite in one direction?

Hi everyone.I need to make a game when u need to avoid some obstacles(red lines) that are part of the whole line.Now,i finished a part of the game ,but the big problem is when i try to make the line moving infinite at a constant speed in one direction (up or down) I want to make all lines moved in one direction constantly at infinite,but i don't know how to do this. If you have any idea please help me. I really need to know how to do this.