Slide out front table 2016 Lunar Cosmos (Quasar)

Hi all,

I have a 2016 Lunar Cosmos (quasar). My question concerns the slide out table which is under the front window. 
 The upper surface should have a little up and down movement; enough to drop behind the lower surface when you slide it out. The previous owner has done a bodge job and screwed the upper surface directly into the frame so that it is fixed in the upper position. I can see on each corner of the unit tall drilled spaces where fixings should fit that would allow the up and down movement, but these fixings are missing. Does anyone know what to call these fixings so I can search for them?

 All input and advice appreciated.

Thanks.