A common example is where pipes, conduits, structural beams and other such infrastructure must penetrate a fence or similar barrier and may provide a means to circumvent the barrier. A collar of large spikes approximately  long is fixed around part or all of the circumference of the penetrating element.
A frequent scenario includes pipes, conduits, structural beams, and other infrastructure needing to traverse a fence or equivalent barrier, which might serve as an entry point. A circular arrangement of large spikes about in length is attached around part or all of the circumference of the penetrating element.