Have done bunches of step flashing. I know they sell prebent 5x7's but usually just make my own since it's only my time and usually have a roll of 10x10 or 10x14 aluminum around. Have always made them 5" up the wall and 5" on to the deck in 7" lengths.
Anyway, I was at the Borg and see they sell prebent ones. These suck because they are only 4" coverage. But I happened to notice they sell 5x7 flat alum plates...like one leg of of the ones I make. Never was sure what these were for.
Today I happened to be thinking while looking at the existing step flashing on a roof I'm doing (the last of 8 planes on this 26 sq house). This house has vinyl siding. The bottom channel of the siding is nailed to the vertical wall right at the flashing so you can't just slide the old flashing out and slip new in. Either pull the channel off and a row of siding to replace the flashing or just cover the nailholes from the old shingles in the flashing roof leg and reuse as is.
Now I'm thinking about these 5x7 flat alum plates that are with the prebent flashing. Are these things meant specifically for this situation? Just put it over the roof leg of the old flashing to cover the old holes? That's all I could come up with. Doesn't completely make sense since water could get between the old flashing leg and these plates.
I prefer to take the time and put new step flashing in. Pulling the siding channel and a course of siding isn't gonna take that much time.
Curious Al....