Suckers onto the window glass. It's fab, but I have been told by frineds that they can't get hold of them - there seems to have been a bit of a run on them since we were evangalising about them on here a few weeks ago.
Just checked the website and it says they are in stock. Ive not heard of these before- sounds great. Ive got the curtain type but they keep coming loose....am off to check measurements of DS's bedroom window now LOL
We have baa baa blackout blinds for holidays, they attach directly to the glass.
When combined with curtains they are great but they IMO aren't made of a blackout material. I did contact baa baa about them and they said they were "travel" blinds, they are good but not like covering your window with actual blackout material.
We have blackout roller blinds and I roll them down a bit further than normal and blu-tack them to the glass in my son's bedroom to stop the light but we also have blackout lined dark curtains too. Light still comes in through the top but none from the sides.