Given that my flash is covered in velcro for attaching gels, I thought it would be possible to create barn doors that can be attached directly to the flash. All I needed was a hinge mechanism that would allow the doors to be set in different positions.
I realised that it would be possible to create the barn doors using some stiff card for the door and cinefoil as a hinge. Cinefoil is heavy duty black aluminium foil use on film sets to make light modifiers, I had some handy, but you might be able to use stiff silver aluminium foil.
The neat thing about this design is that the DIY barn doors are stored flat, take up very little room in your bag and they don't all have to be attached to the one flash, so you could split them between two or more flashguns if you want to use them as flags.
For your next trick you will need to cut some strips of foil to wrap around the cardboard. I found that wrapping a two foot strip about an inch wide around the two pieces of the hinge gives enough stiffness to make it work nicely. The image on the right should give you an idea of what I mean. Then you can carefully wrap velcro around the whole thing to make it look
like a sticky mess professional.
light pattern it produces compared to the ebay doors and of course it is way cheaper and more portable than the ebay doors. It would be no hardship to keep a set in my camera bag. I think there is more tinkering that can be done with these. It might be possible to refine the shape of the doors to create wider beams or a double hinge to allow the doors to unfold to the same dimensions as the ebay doors. With something this cheap and easy to make, experimenting won't cost you a lot. Let me know if you have had a go and managed to improve on these doors.