[Billdit]

Hi,
I don't have a photo to hand at the moment, but basically it doesn't have a means of securing ithe flap in place. What the manufacturer has done is to incorporate a sewn in pocket that is the full width of the roll down flap, which you slide a metal rod into to add some weight to the flap. I can get you some pictures later today if you like.
The trailer (the one my tank is on) is my own design and I used some suspension units from a cross-rc trailer.
I can do a basic build thread if you want to see how it came together.