for my darkroom door
i use black canvas from the top of the doorframe
to the ground
it is wide enough to overlap the sides of the "doorframe"
and it is long enough that its weight keeps it in one place.
i think i have 3 or 4 layers ...
it could easily be done without any nails or screws ( although it would make it better that way )
by getting some heavy curtain rods and putting them up to the top of
the doorframe snug against the fabric.
i've used a door light this for 8 years without any problems ...

good luck!

john