So at coordinate x prime, of the right side of the garage is equal to I, and it too of course will be moving at speed v, at the same speed v. So its world line is going to be a parallel line here. this is the world line spiritually drawn, of the right end of the garage and as you've, as I've drawn it you can definitely see that at t equals zero, when the left end of the garage of the ladder enters the garage, the right end of the ladder has not yet exited the garage, and therefore at this point and in fact throughout the time that I am going to mark out here. 