We have been using blocks in Adho Mukha Svanasana (downward facing dog). I’m finding it very interesting. It makes it possible for more weight to go back into my legs. My hamstrings are so tight that I am usually totally bearing down in my arms. My heels never even come close to the floor. In this variation, I can get closer. I often use a strap around my elbows to lessen the strain on my arms. It helps, but it’s a hassle if you’re doing variations and/or sun salutations. It keeps getting in the way.