advise sill covers fitted

On my last MOT the only advisory was "advise sill covers fitted". Has anyone any idea what this means? I guess I just need to ask the garage, but thought I'd try here first. It's a 2013 Jimmy. 

Any help would be appreciated.

Happy New Year!

It means the tester was in CHA mode (Cover His Arse), he's saying there were covers on the cills which means he is unable to test the integrity of them. On the training they are now told to make a note of anything they can't test, plastic covers etc.

He's right ^^^^, CHA mode in action. 
It's a bit hit and miss with testers, if they aren't sure they now mark it as an advisory, or not, depending upon which way the wind is blowing.
Once got one for the tow bar as the removable hitch wasn't fitted, so he couldn't test it. It's passed every year before and since since with no advisories, still with the hitch removed.
He obviously didn't mind the plastic sill covers!

The previous owner to me kept the seats folded down and a dog crate in the back. That went down as a note/advisory that the inspector couldn’t check the rear seats or rear seat belts.

It’s for this reason I take my cargo area board out and put the seats up for the MOT, then put it back afterwards.

Robin

Thanks so much for the replies!