The plastic "fit in hole" shelf-supports come out too easily, with the
result that if someone bumps it,the shelf falls out, along with
everything on it.

Each support works by pushing (inserting) its 1/3-inch-long cylinder
part into the predrilled hole; four such holes, each with one of these
plastic inserts, support the four corners of a shelf.


One way to keep a support from slipping out of its hole would
be to glue the cylinder part into the hole.

Disadvantage: you can never get it out again, should you
want to change the spacing between the shelves.

Question: is there some kind of a WEAK glue that will hold up to a
point, but then will break its bond, allowing you to remove the
plastic support?

Thanks!

David