Rugby shapes split into two problems that don't move together — where your eight forwards stand at a scrum or lineout, and how far your seven backs spread across the pitch on attack — and this editor lets you place both groups independently instead of dragging fifteen interchangeable dots.
An attacking-width backline stretches all seven backs across the pitch to create overlaps out wide — it needs quick, accurate passing under pressure or the width is wasted. A defensive drift line does the opposite job: defenders slide together, passing the attacker on to the next player inside-out, betting on shepherding the ball to the touchline rather than making an isolated tackle. Set-piece shapes (scrum, lineout launch) are about a much smaller decision — where exactly the pack and the first receiver stand the instant the ball comes back — and that's precisely what's hardest to communicate verbally and easiest to get wrong from a diagram that treats forwards and backs as one interchangeable group.