My casework method...

Module 3 Day 10 Your Turn Part 3
Ok, I admit I didn't do the onlytoprow method like Prof Loh did, but I did a similar method:
Like him, I discovered that horizontal 1x3's come in 'clusters', meaning that I can see them as one group.
My casework was based on the # of vertical rectangles: If there're 0 vertical's, then there are 3 'clusters'  1 way
 If there's 1 vertical...wait, that's not possible! You can't fit 3's into 8!  0 ways
So the number of vertical's must be a multiple of 3...  3 vertical's, 2 clusters  10 ways
 6 vertical's, 1 cluster  7 ways
 9 vertical's, 0 clusters  1 way
Total = 19 ways

@rz923 This is really nice! I've also linked this to the Your Turn Part 3 lesson.