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 common instance involves pipes, conduits, structural beams, and other such infrastructure needing to pass through a fence or similar barrier, potentially serving as an entry point. A ring of large spikes about in length is installed around part or all of the circumference of the penetrating element.