Consider an observer equipped with a good ruler and a rod. This observer measures the length of the rod and finds it 30 cm. Now this observer with his ruler and rod rides a space ship and moves with a high speed. He then tries to measure the length of the rod using his ruler. According the SR, the length of the rod is expected to be contracted, but he will measure 30 cm because the ruler will also undergo length contraction with the same proportion. Therefore he will not measure any length contraction!! How is this possible? Or length contraction is a "theoretical" consequence of SR which could never be "measured" - since the tools of measuring will undergo length change with same ratio?? Thanks to any ideas.