If your character is walking backwards alongside a wall then you turn your head towards the wall you will briefly clip your head through the wall, seeing through it.

In the chance you can't reproduce, here is some additional info that may be a factor: 1. You may need your FOV to be a few ticks lower then the max. 2. You may need to stop moving when you turn towards the wall. 3. You may need a 2 handed weapon in hands. In my experience i can do this everytime without an issue, i imagine people are already exploiting this.