Bowed fence
A bowed fence or bow fence system is a type of panel fence that curves inwards. It is usually very high - in excess of 3 meters measured from the ground to the top of the curve, and is usually used around high security sites like maximum security prisons.
Bowed fence systems are very complex to install, and often require specialist equipment to manufacture - including a steel bender that is usually used for railway tracks!
This fence is exceptionally hard to climb, because it is not only built using 358 mesh (which has very small apertures) but anyone on the inside of the fence also has to contend with gravity - and often razor coils when they reach the top of the fence!