This experiment consists of a metal grill that can be twisted to create torsion waves. The waves will reflect off the far end of the grill in either a free or fixed end fashion but the difference is difficult to see unless the students know what to look for exactly.
Image from  http://www.phys.ufl.edu/demo/3_OscillationsWaves/B_WaveMotion/FreeFixedTorsionWaves.html
[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=1545.0;attach=2080[/img]