Some time back I made an awning lock from a steel rod and put a 4" bend at the top to insert into the awning tube. I strapped it to the awning support using Velcro straps.
Today I happened to look at it and over time the rod had moved back on the support until it was almost out of the roller tube!
I went back to Lowes, got a new rod, and made a new one with a 8" bend at the top to go into the roller tube. That way, even if it slides back on the support there will still be at least 4" inside the tube.
Take a look at post #30 & 69 below
Opened awning while driving I-75