How to attach timber extension to Colorbond fence?

[SallyBee]

How do I attach  2.4m long X 500mm high timber fence extensions to the top of a colorbond fence? Should I cut off the shorter legs and use the longer legs to screw the extension onto the colorbond fence? Which screws (and what length) do I need and how do I use them? Thanks

 

?

[Jewelleryrescue]

Hi @Nailbag 

pre drilling holes  would  work as a metal screws bit not meant for wood better to use wood screws and  drilling/screwing over head always  harder.