Why do we need these lines in football like the D-box,center

Inside the new AAF defensive formation rules – Football Zebras

Defensive Line Techniques & Alignments In Football - vIQtory Sports

Football Field Dimensions

The Role of the Soccer Center-Back

Why do we need these lines in football like the D-box,center circle,and everything? Give explanation to all details in fifa? - Quora

Penalty area - Wikipedia

Why does a football field have a circle in the center? - Quora

U.S. Soccer Numbers Explained

How big is a Footbal field? Find all dimensions for a field here

Offensive Line Drills - Center Blocking Technique - Football Tutorials