Four offensive players have to line up at stake of scrimmage. 3 defensive players need to be down linemen (in A 3 of four-point stance). A person linebacker may well blitz on both side of the center. Defensive linemen have to line up no wider than shoulder to shoulder ("shading") https://leisurecityguide.wordpress.com/2024/08/29/the-thrills-and-benefits-of-indoor-football/