You may have read references on this site comparing the goal nets of today to trampolines, but it's a metaphor to describe nets stretched square and so taut they cannot retain the ball. No club actually installed trampolines for goal nets. Except Schalke...
In the mid 70's they rigged a system to suspend the goal nets at the Parkstadion by installing a full goal-sized frame behind the goals and attaching the nets to the frame with trampoline springs.
You can guess at the aesthetic affect...
