Core Questions for Mechanical Engineering

Hello, I had gone for an interview at J.B Steel company. At first there was an aptitude test, which was cleared. After that there was a GD round which was also cleared. And at the last there was a HR and Technical round where the HR manager asked some questions to me.3 questions were normal which I had answered but after that the questions were quite different from conventional ones.He asked me about the working and how to repair Hydraulic Jack. I answered about the working but about repair I was not knowing. Pls help me out to answer the question.