Inside table holders. How do they work?

[bastos]

Hi all,
I have a 1999 van with a rail table with some kind of pins in the kitchen unit, but those do not stay in place. What am I missing from the setup? I don't even know what to look for. Is it some magnet, or some rubber things? The kitchen unit has 4 holes, and none of them holds the table in place.
Thank for any suggestions.