More 12.5" Block stuff.
I had to do this one and rip it out a couple of times. Got to get the size right or it won't fit nicely with the other blocks. I posted the right numbers on the photo a couple posts up.
The 2 major things to check are; after you have finished and squared it up to 12.5" X 12.5", the diagonal measurement across the 3 dark squares should be 12". There should be 1/4" of the large triangle at each corner for seam allowance.
Jupiter