Will start again (without the double click!)
Our solution was using a dark teal coloured stretchy velvet velor material ( like those velor leisure outfit ) and made regular curtains with a rod at the top and a line of stretch cord at the bottom attached to the walls.
When we want total blackout as seen from the outside, we draw and tuck the curtains into the cord which holds the curtain tight to the inside wall and allows absolutely no light
and no images to be seen from the outside (Walmart parking lots for instance)
It also works to keep the high noon sun at bay.
I even used a large piece to act as a curtain across the bed ( like a train berth) when one of us wants to read at the table and the other of us wants to sleep in the dark.
Miserable stuff to sew however!