How to blackout a large bedroom window on a budget

windows

I am renting an apartment that comes with blinds – that I can not remove or replace – but they are not very effective at blocking the light in the morning.

I can not remove the existing blinds
I want to keep the room light during day so no sticker or dark foil
my budget is limited and I would like to avoid buying and installing heavy curtains.
How do I darken the room on a budget? Any DIY tips are welcome.

Someone suggested pinning fabric inside the blinds but I am not sure how effective that is? What kind of fabric should I buy to try this?
This is for a baby room, so he doesn't wake up with the sunrise 🙂

Best Answer

A sheet of cardboard cut to fit the window frame tightly. With a small finger hole or notch cut out so you can pull it out easily. Thick cardboard would be best so it doesnt bend.

Practically free, blocks all light, does no damage, and can easily be removed in the morning and put back in at night.