There is not much to this instuctable, but hope it was worth sharing.
I needed to carry a long ladder outside the car, but I don't have any cross rails for my fixed car mounted roof racks.
A quick Google search revealed prices of $75-$350 for a set of rail to fit.
I went to look for a couple of pieces of scrap wood laying around my place, but none of the short ones were long enough, and it seemed a waste to cut down the really long ones.
I did find a 3 metre long piece of 25mm (1") PVC pipe sitting outside in my pile of junk (as can be seen by the amount of dirt on the pipe).
I cut it into 3 x 1 metre pieces, and used 2 zip ties on each end in a cross pattern to hold the pipe to the rails (12 ties in total for the 3 rails).
With the zip ties tight I could not move the pipe in any direction.
Note: I could have used more zip ties or u-bolts for safety, but as I lashed the ladder mostly to the fixed rails, I didn't feel it was necessary, as the rails were really only keeping the ladder off the roof. I did a 100Km round trip without any issues or slippage. On my return, I removed the zip ties and was easily back to normal.