Method for compound angles on a miter saw

Since I want to mke a carrying box for my small gardening tools (and cannot justify a Sussex trug for this) I plan to make a sort-of shallow planter ,or butler's tray, with a central handle. Their corners got me interested in compound angles - and I was hooked. I found a post in this group writen by Elmer Gilman in 2000 where he describes a procedure to make compound angles (such as at the ridge end of a hip rafter) using a miter saw, NOT an (S)CMS. Ref:
I hope it is not a joke, because I do not understand it. I quote a bit:
" on a 4/12 hip roof the saw angle is 22.5 degrees . . . and place the crown side against the fence ( this will be the top edge of the rafter) pivot the bottom of the rafter (the edge facing you) up towards the fence keeping your finger behind it when you make contact with the fence. set the saw to 22.5 degrees and cut the board. You now have a perfect 4/12 . . . hip rafter prow cut. " Unquote. Can anyone explain that finger bit ? Sounds, well . . .
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