Squat form guide

At the end of my work shift I have the gym to myself .When squatting I stand inside the rack and back up to the upright letting the bar make contact with it. I align my toes with a line in the carpet so the bar is midfoot. Of course it makes a scraping sound as I go up and down but i can live with that. I thought it would help me groove that vertical bar path that we want… Harmful or helpful, your thoughts please?

It’s probably not helping that much, as external cues typically work when the feedback they impart doesn’t change the desired movement pattern.