Blocking your calendar as a productivity hack

I read a post from a famous builder noticing that blocking your calendar often is 10x more impactful than having a to-do list. So I took an experiment with my own calendar view and my take on this is that it`s kinda true when I don`t have a full scheduled calendar day/week I`m way more productive and have way more time for the important things, I also figure out that blocking my calendar is boosting my time-management skills. Funny how obvious that was really...I`m thinking what is your take on the topic, and do you use some helpful tools for calendar blocking?