Topic of the day: museum wax or putty. This “stuff” works and saves your glass items from crashing to the floor. Really it does stick with no damage to your items… All my vases and anything fragile or that I do not want to break is “fastened” down in this manner.
When I changed out my mantle to camels and peacocks, I had to find new places for my Mayan/Aztec/Olmec replicas (via Mexico shopping trips). So they end up on top of the new bookcases on the side of my office along with casts like the dinosaur tooth as well as fossils. The tops of those bookcases are now crowded.
Only problem is the fragile items could fall easily in an earthquake: why the topic of museum wax came up. Below is what brand I use and for me they work….
Oh also be sure to bolt the bookcases to a stud in the wall using angle brackets, keeps those from falling in case of an earthquake or kids from climbing… saves accidents from happening. Screw them into the stud and into the bookcase, dresser, whatever… be safe not sorry