Securing windows

Does anyone have windows similar to these? How do you secure them so you can open them at night and they do not slam shut in the breeze? The windows push objects off the window sill intended to hold the window open. Ideally they windows need to be ajar, and not fully open either.

Use Screw Down Adjustable Casement Window Stays.

Would there be enough clearance alongside the window locking mechanism to screw the window stays?

Try these, they are also lockable:

They look a bit like a medical apparatus Geoff :wink:

We just use a length of wood (30x15mm) wedged between the windows when they are open.