The two strips on the side slide off to allow the top and bottom parts to come apart. Most likely problem is not the switch itself but the plastic switch actuator. You can get this part at any vacuum shop. It is a common issue with this model. This repair is not all that fun for the typical Do-It-Yourselfer. The machine is a bear to get back together. Good Luck Mate!
www.bobsroswellvacuum.com, September 2008