I haven't seen this before. I have devised a way to accurately and easily align plywood panels when scarfing them together. I like to mark out and cut the panels separately to make the most out of a sheet of plywood and have found it a bit fiddly when aligning the pieces to join them.So what I do is make an Index Mark on both ends of both panels 2" up (or whatever measurement is convenient) from the baseline when marking out and then I find it quick and easy to align these marks using a laser line, or a string line.Please see attached diagram.
Robert