When parachutists need to leave an aircraft en masse, there is a danger that some chutes won’t open, even when activated by a static line.
The usual rail to which static lines are attached is, in today’s invention, extended from the rear of a transport plane. There would be several such rails in parallel.
This allows each jumper to have his chute opened by the static line and the airflow around the fuselage, in the usual way.
If it fails to deploy, which can be automatically sensed as low tension in the line, the jumper can be brought to a halt before leaving the rail and the chute jettisoned.
Whilst he was being pulled back on board, the next parachutists attached to that rail would unclip and reattach themselves to another rail.