aye, a piece of flat black plastic slides into both the back and the lid. i think if the frames were heavier aluminium the weight itself would keep them down, but as they are so light and the lids don't naturally fit square onto the frame, the wind gets into the wee gap and woosh !
nice idea if they were more substantial but i think as we said at the time ........ what do you expect for twenty notes.
still can't find a matching hook :-\ but it's only really the side i've weighted that lifts anyway. had a look in there today and the lilies are turning into triffids !!!
:o