To clarify, there are apparently two different systems. I seem to have the same kind that ComPH has - the lower "clip" is a fixed hook, tongue, whatever, that faces horizontally. This also sounds like what Ziemas has. If that is the case, ComPH has described it, this "clip" simple hooks one of the rack uprights. Combined with the top clips it seems to be a pretty secure system; I have not had any problems with security. However, because it is fixed, it can seem like a problem if your rack doesn't have an vertical in exactly the right location. On right (drive) side of my IRT rack I attached a snug loop of inner tube vertically to create a faux upright which I hook to. Initially I used a little loop of innter tube slipped over the hook, around a stay then back around the hook. This actually worked pretty well. On the left side I clip the top clips then force the lower part of the pannier back to hook the rear upright. I don't have to force it too far, and it makes a nice snug attachment. Although secure I am not particulary thrilled with this mounting system. I do like the bags, and I could retrofit an Arkel system if it really bothered me.