Four offensive players have to line up on the line of scrimmage. Three defensive gamers have to be down linemen (in A 3 of 4-place stance). One particular linebacker may blitz on either side of the center. Defensive linemen need to line up no wider than shoulder to shoulder ("shading") https://leisurecityguide.wordpress.com/2024/08/29/the-thrills-and-benefits-of-indoor-football/