How do I attach the heater hose to the blower?

The hose that attaches to the blower on the right side of the car keeps coming off. I have put the hose on at least 5 times over the past year or two, but it does not stay on for long. I looked up into the firewall area and the hoses seem to be installed with a clamp (turn key style like the two used to keep the air filter hose on in the engine compartment.) Is there a secret as to how the hose stays on the blower, or do I need to use a clamp? The left side hose and blower does not have a clamp and has never come off. Thanks for the help.

Ken
308QV