Fixing a threshold strip

[alex1b]

Hi, does anyone know how I could fix the wobbly threshold strip on my front door? Sometimes it's a bit loose and this stops the door closing properly, which isn't good! I've attached a picture. I think it's adjustable, and that the middle strip you can see should lift up so I can access screws underneath; I've tried prizing it with a screwdriver and although there's a little give, it feels like it would need a hell of a lot of force to do something and might just break. Any suggestions?

Thanks!

 

[daviddave]

it feels like it would need a hell of a lot of force to do something and might just break. Any suggestions?

Hi,
don't force the middle strip, there may be another fixing system of the threshold strip.

 

[alex1b]

Hi,
don't force the middle strip, there may be another fixing system of the threshold strip.

Any clue what kind of thing it might be? There's no visible fixture…