There are three velcro straps on the top/bike side of both panniers. the centre strap of both are underneath the seat, you lift seat (obviously) and postion bags at each side , and attach centre straps to each other, positioning them at the handlebar side of the locking mechanism for the seat. Well I did anyways and I think once the seat is put back down again, the part underneath seat that connects to the lock will stop bags from sliding of the back of bike.Do they sit well and securely without a brace of some sort behind them?
Got to be cheaper than the yammie ones