Light fitting cleaning

[PhilMary]

My Autocruise Select 144 has a light above the sliding door. I want to open/remove it to clean out the muck. As there is no visible screws I thought to ask your advice before ripping it to bits.

Any help would be appreciated.

 

[TUCANO]

No idea but if there are no screws does it not slide up or down for removal.

 

[PhilMary]

I'm reluctant to push or pull too hard in case I break something!!