Hey Chirone...I dont know what the hell Im doing BUT...I did a mountain surface...then drew a curve across it (for the planks) then created a poly rectangle and tried to extrude along it...it wouldnt do it...hmmm BUT I then turned the curve into a B-spline...then extruded the face and it worked...kinda...I got some funky stuff happening...Im at work so gotta go...so I got it to work sort of...sorry I couldnt help mate.

cheers bullet