They secure using the rixen & kaul klickfix clips that a few things use, you hook them over the panner rack top bar and 2 latches spring out to secure them. to release you press the red button down and pull upwards
I am missing the 2 stabliliser hooks though that run on the horizontal rail at the bottom half. These arent essential and i removed and lost them as they would dig into me when i had the panniers over my shoulder, if you can meet in the middle at £35 they are yours delivered anywhere in the UK