A box strapped to the seat with bungee cords slides at the first hard brake; the lid works open, containers tip over, and a box with its lid ajar no longer insulates anything. That is why the box is bolted to a carrier plate that is itself bolted to the bike. The plate carries the load into the frame and the box sits flat.
- Fit the carrier to the attachment points meant for that motorcycle model, using its own bolts, and stay within the load the carrier allows.
- Bolt the box to the plate; the lower and further forward it sits, the less it affects steering.
- With the box empty and then loaded, check that nothing touches the wheel, exhaust, suspension or controls, and that the lid does not hit the seat or rider as it opens.
- Put heavy containers at the bottom and light ones on top, and fill the gaps.
- After the first week, tighten the bolts again.
On a motorcycle used for courier work in Türkiye the box is also a registration matter. Article 24 of the Road Transport Regulation (as amended on 15 May 2025) requires that a motorcycle or moped entered on a P1 or P2 courier licence, if it carries a transport box, has that box comply with the relevant rules and entered in the vehicle registration records; the motorcycle itself may be no more than ten years old. The thirty-day rule for modifications sets how quickly that entry has to be made.