I've been making disappearing four patch blocks lately. Today, I wondered what it would look like on point, so I cut the corners off so the "middle cross" now becomes corner to corner "X". It would be easy to do by making an hourglass block and cutting it like the D4P. I thought I had come up with something unique but googled "disappearing hourglass". Bad idea as there is another block by that name. I googled "Disappearing half square triangle" and danged if someone hadn't already thought of it And she copyrighted it under the name "Arrowhead". From what I could find, she uses some kind of stack method, not the recutting like D4P. And then someone else made a similar block called a "Disappearing four patch with a twist". She didn't copyright hers but started it like the D4P and then made diagonal cuts instead of horizontal.
Here's where I am confused on what exactly the first designer copyrighted. According to the copyright information I found
at modern quilt guild: ", but if the original quilter’s work is still recognizable in your version, it’s a derivative." I recognized "Arrowhead" immediately as being a derivative of D4P. So is the copyright on the block itself or the technique used to make the block?