The abutted surfaces of the square C-shaped beams of the upper H-beam and the lower H-beam have respective intermediate portions (120, 220) which protrude and contact each other.

The lifting crane (12) has a horizontalcrane beam (14) carrying the man overboard device.

The clamping portion (12) is arranged to be clamped to a scaffolding pole, either an upright standard pole or a horizontal ledger pole.