How to hang blinds in window with thin board facing?

[Fab5Freddy]

I dont quite know the name of the bit of the inside window upper sill/surround at the top , but I am referring to that part. (ie NOT the window frame)

I have a wide downstairs window (1760mm) that has 2 opening windows either side and a central (equal part) that doesn't open. So, in short, it has 3 parts.

In order to get a blind to fit and look right, I need to get 3 blinds of equal length . BUT the top part of the surround/sill is just a thin piece of plywood covering the rsj type metal window support.

So, the fixings for the blinds won't have anything to get a form grip on to screw it to.

I am thinking the solution might be to wedge a piece of wood maybe 1/4 inch thick and as long as the window upper sill length, and then attach my blinds to that.
It doesn't sound like the best solution but I cant think of how else to do it with the least effort.

Can anyone suggest a good solution to this?

Thanks in advance

 

[foxhole]

Screw into rsj

 

[Fab5Freddy]

Screw into rsj

Not sure I will find a screw long enough and wide enough to actually get through the blinds attachments clips , as the screws provided with it are pretty short and thin. I think I need some other solution , but thanks for reply

 

[foxhole]

Not sure I will find a screw long enough and wide enough to actually get through the blinds attachments clips , as the screws provided with it are pretty short and thin. I think I need some other solution , but thanks for reply

You don’t use supplied screws.Only needs one screw in each bracket .

TechFast Light Duty Self Drilling Torx Roof Screw 4.8 x 38mm | Toolstation

Self drilling screw with countersunk head and wing tip. For fixing timber to light section steel. Salt spray tested to 1,000 hours. Torx bit in each pack.

www.toolstation.com

 

[Fab5Freddy]

Many thanks @foxhole