What locks on-chain?
The wallet that creates this job is the shipper. In one transaction the Pelusium contract splits your SUI into freight escrow (courier payout on delivery, minus protocol fee) and optional goods escrow (seller payout on delivery when you enter goods amount + seller address). Both balances live on the FreightJob object until delivery or refund. For shop buys delivered to your SSU, the shipper is usually you (the buyer).