No locking :-(

Unfortunately, the product is missing the backup, which prevents accidental release of the locking. Has been criticized here in a recession. The bolt is inserted into one of the holes, but unfortunately this may be unintentional loosen again. Especially since the bolt is only slightly "pushed". Then the whole thing crashing in on itself, stupid, when an instrument for several hundred euros then stood on it. Since the diameter of the holes (height adjustment and frame) is different, you can not simply plug a thread and secure on both sides with nuts.
The solution would be simple. Just in the bolt provide a hole for inserting through the hole a locking pin slide .... done. The same method is applied for example in collapsible garden furniture.

The processing of the frame, however, is perfect, very stable and sure. Because of the "collapsing danger" with probable fracture of the device only one star.