How to make cage with bars not mesh

[Kap]

Following my question about a crazy cage for budgies, I have rethought my plans. Most DIY cages (and it must be DIY as large cages seem simply unavailable in the UK). Most plans for DIY cages involve a mesh over a wood frame. How do I make a cage with bars though? Some detailed plans would be helpful. Also, what wood thickness is appropriate for a cage?