IN my case i was wanting to change my OFF-ROAD POPUP trailer to one of these type shore power cables so I can use my idea for manual hook method power change over procedure.
Something like this

Using the short 30A to 15A adapter cable I can easily connect my trailer to my 1500WATT PSW Inverter setup to power up all of my 120VAC receptacles inside the trailer. (Poor man's auto transfer setup)
Just adds more to my style of camping off the power grids...
This is my OFF-ROAD Trailer floorplan I am working towards for my next battery bank upgrades for more AHs...

Roy Ken