I have a picture somewhere. It might be on my website site. The bridges are made of royal icing. And, I have instructions for them. I'll have to check that out. Tape the bridge template you draw over a gallon jug. Tape the waxed paper or parchment over that. Pipe with royal icing. Let dry for several days before removing. You could tape cellophane as that "breathes". Do two parallel lines of royal in brown. Pipe lines in zig-zag formation. When the parallel lines are well dried, pipe the design in royal over that for support. Then, when that as well as the zig-zag lines are thoroughly dried, pipe the royal design over that. In white, it's very pretty to connect the surrounding cakes to the main tier cake. Great when you need extra servings. For the bridge in royal or fondant, it would depend if you wanted it curved and it needed support. For support, I would use pastillage or gumpaste that has gum trag or tylose in it for good, harden support. When you want to have the bridge look of planks of wood that has been put next to each other, just roll out the medium and mark the medium with indentations made with a long, ruler or straight knife or spatula. Then, tint in wood color for the wood grain effects. You can also etch into the medium to get more character to the wood grain effect. To tint, I start with orange and green food coloring as that creates brown. Then, I add brown colors. Next add a clear alcohol and tint the wood with a wide artist brush.