Good morning, Hugh,
I’ve been following the discussion on “indoor concertina wire” and agree wholeheartedly; it’s a poor decision.
A recent writer pointed out that concertina wire, barbed wire, and tanglefoot should be secured to posts of some sort; I concur, and would like to elaborate on that topic.
When I build fences I install a 4 foot wide hinged walk-through gate that, on closing, latches to a removable post. There is also an 8-foot hinged gate that latches to that same removable post, allowing a 12-foot entry for equipment should it be needed. Depending on the fence, and requirements, the removable post is either a wood 4X4 or a 6X6; a 36-inch length of 1/4 inch wall thickness square steel tubing is inserted in a hole and concreted in place, with about 2 inches or so exposed above ground level. About 4-6 inches from the bottom of the square tubing four 1/2 inch holes are drilled through opposite sides allowing for a pair of 1/2 inch galvanized steel rods to go through the tubing and extend about 3 inches from each side. These rods – “post support rods” – both help secure the tubing in the concrete and form a base for piece of stainless steel as a “support plate” to support the wood post. The stainless steel can be from 1/8 to 3/16 inch thick; thicker is harder to bend, and it’s not under any stress. Use a piece about 1/2 inch narrower than the inside of the tubing and 3 times longer than the tubing’s inside dimension; bend it in a wide U shape about 1/2 inch narrower than the inside of the tubing, so the “legs” extend down about 4 inches or so. The space between the sides of the plate and the square steel tubing allows for drainage, and the shape allows dropping the “platform plate” into the tubing to rest on the 1/2 inch rods after installation without it becoming misaligned. A note: stainless is non-ferrous, so it cannot be removed with a magnet if you get it wrong. A shop vacuum with a PVC pipe extension can usually be used, however. The support plate is necessary – without it the two rods will indent the wood post and over time the post will slowly settle into the square steel tubing, requiring constant readjustment of gates and latches. If necessary, the 2-3 inches of exposed square tubing can be drilled for a lag bolt to secure the removable post. Pro tip: it’s much easier to drill that hole before the tubing goes into the ground.
A little sanding or planing will be required to get the wood post to fit easily into the square steel tubing and be easily removable, giving you the option of a 4 foot (or wider) walk-through gate, and 8-foot wide vehicle gate, or a 12-foot wide equipment opening.
As for perimeter defense, the same technique can be used elsewhere, using shorter lengths of square steel tubing. A 12 to 18-inch length can be positioned wherever you need to control movement, and set flush with ground level. Depending on the installation and intent, it may be possible to skip the concrete step. Only one 1/2 inch diameter “post support rod” is necessary for these, and since gate latches aren’t involved, don’t bother with the stainless post support plate. To avoid having an open hole that could be stepped into by people or animals, drop a length of 4X4 (or 6X6) into the square tubing, trimmed flush with the ground so you can mow right over it. Removal is accomplished by screwing a lag bolt into the end of the wood post and pulling it out.
When circumstances dictate, a wood post of suitable size can be dropped into the below ground square steel tubing and concertina or barbed wire attached to it. A 3 foot length of 6X6 1/2-inch wall thickness flush-buried square steel tubing, set in concrete, will provide enough support for an inserted 6-foot length of 5-inch, 1/2-inch wall thickness, square steel tubing to resist “dynamic removal”; I’m not aware of any readily available passenger vehicles, including pickup trucks, that are capable of driving through a couple of closely spaced steel posts of such size. The inserted post (think two square steel tubes telescoped together) can be secured with wooden wedges driven between the sections. The wedges and smooth sides of a steel square post will largely prevent pulling the post out by hand, especially true when the homesteader can provide armed overwatch of the posts.
The same technique may be used with lengths of round steel well casing and lengths of telephone pole. Utilities replace poles due to age or vehicle accidents, so they’re often available free, and while the buried portion may have some rot, the above ground portion should be fine, and since the entire pole has been treated to resist rot, the unrotted sections should provide many years of service, even when buried.
In those areas where more permanent vehicle movement prevention is desired, a 10- or 12-inch diameter pole section buried 4 feet in and extending 24-28 inches above ground, on 3-foot centers is effective. A second row, positioned a few to several feet behind the first and staggered to be spaced in the front row gaps provides an additional level of security.
A suitable type of grass or plant that can grow high enough to hide the posts, preferably a plant type that doesn’t require maintenance, can provide beautification while concealing the fortifications. Pro tip: apply copious amounts of barbed wire to the posts before planting the greenery, and note that small coils of concertina wire can be positioned between the post rows and secured to them, which will become quite unobtrusive when the plantings grow over them.