Edge
Where the circle ends
A step-out is a small score and a large piece of information. Someone ran out of mat.
The red line is not decoration. Step on the wrong side of it and you have handed over a point, or you have been pushed there by someone who wanted that point more than a throw. Both versions look similar from the upper deck. They are not similar.
Edge wrestling is a habit, not a technique with a name on a poster. One athlete keeps the circle at their back so a step becomes a score. The other keeps it at the opponent's heels. The feet do the talking. The hands are busy pretending this is still a tie-up.
Stand where you can see the line and the back foot at the same time. If you can only see the line, you will call everything a push. If you can only see the foot, you will miss who made it move.