Welcome to JOF
I believe the Hummingbird's have what is referred to as a "in-wall" slide manufactured by Lippert (Schwintek).
If my 'assumption' is correct the following video may be helpful, otherwise I'm sure another JOF member will steer us in the right direction. The video is dated so there may have been some product updates depending on your model year Hummingbird.
Bob
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2016 GM 2500HD 6.0L/4.10
2018 Jay Flight 24RBS
2002 GM 2500HD 6.0L/4:10 (retired)
2005 Jayco Eagle 278FBS (retired)
1999 Jayco Eagle 246FB (retired)
Reese HP Dual Cam (Strait-Line)