Great little device!
I am using this with a small camcorder attached to a microphone stand and it works perfectly for what I need.
Firstly, the relevant angle you want is set, then the ball-head adjuster locked with the plastic wing-nut (metal threaded), keeping my device firmly in place - and, as an added bonus, the upper locking screw (between camcorder and plate) has a rubber cushion to prevent any marking of the camcorder/device used keeping it very firmly in place.
All in all, a handy little device, which is very well made. I would have no hesitation in recommending this piece of equipment to anybody!