I sometimes pin the first block in each row but I hadn't thought to put a pin in the left side of each pair. I've had to use the seam ripper many times because I have mixed the pieces up.
I also have wooden clothes pins that I will need to try as my markers. Then I can decide if I like pins or clothes pins better.
I do sometimes remember to take a picture of the design wall pattern before I start to stitch. It does help.
Connie