We rencently completed a Study and found this type of fencing very useful with Tresspassing in the Rail Corridors.
Expanded Metal Mesh
Diamond Mesh is available in both medium and high security grades. It is made from special carbon steel,, stainless steel, or aluminum to increase tensile strength, with diamonds small enough that it is virtually impossible to cut, climb or crawl under. The primary purpose of expanded metal mesh is to create a physical perimeter barrier. Basically, expanded metal is a solid sheet of steel that is simultaneously slit and stretched into a rigid, non-raveling open mesh whichtakes as many as 72 individual cuts to create a 36" hole