Tree Pinning: The Art of Silent Spiking (Ecodefense)

The following is part of a series of posts converting to html the monkeywrenching tactics in Ecodefense: A Field Guide to Monkeywrenching (3rd edition). See also the PDF of the book.

Just as spiking is named for the spike-like quality of the fifty and sixty-penny nails used, so “pinning” is named for a lowly steel pin which, buried in the tissue of a living tree, is designed to wreak havoc with the butchering blade of the sawmill. As levels of protective security increase to stem the swelling tide of tree spiking, silent new methods will become necessary for those courageous enough to infiltrate the guarded stands of condemned trees. The loud ring of hammer on spike is replaced by the gentle hum of the cordless electric drill as it creates a small cavity for the insertion of a steel pin.


Because the basic equipment for tree pinning is more expensive than that required for spiking, it is wise to “shop by phone” and get the best price possible. Drill prices, for example, can vary as much as $50 from one store to the next.

Drills — Many models and types of cordless electric drills are currently available, but the best, in terms of torque and price, are probably those manufactured by Black & Decker. Their basic model 9020 sells for $25 to $40. Its slow speed and limited battery storage capacity allows for drilling only 15 to 25 holes, depending on the toughness of the wood; but, you can buy three or four of this model for the price you’ll pay for the vastly superior model 1940 ($80 to $100). The model 1940 will drill twice as many holes as the 9020, and will do so more quickly due to its higher RPMs. It also has a detachable power pack that allows you to plug in a fresh set of batteries. The battery packs range in price from $25 to $50, but you may have to check with a considerable number of retailers to find one who stocks them on the shelf. Do not order them from the manufacturer unless you can have them shipped to a trusted friend who lives far away. Also, never return the warranty registration card to the manufacturer since this creates a paper trail which could be of great assistance to Officer Dogooder and his trusty bloodhounds.

Finally, read the instructions that come with your drill and follow them to the letter. This is your best insurance against equipment failure.

Drill Bits — Use only high speed “twist” drill bits of a type normally used to drill through metal. The flutes and grooves in this type of bit (unlike the wood bit) force the sawdust debris out of the hole. On the first try, a twist bit can drill a 4 to 4-1/2 inch deep hole. A second effort in the same hole (after clearing out the sawdust) can double this depth. Usually, however, it is not necessary to drill in more than 4 inches past the bark to accommodate a pin of up to 3 inches.

Apron — A simple cloth apron makes a handy pin holder. It also allows you to wipe your gloves clean (of silicon — more on this later).

Pins — At a welder’s supply, buy one-quarter inch steel welding rod. It comes in thirty-six inch lengths, two rods per pound, at $1 to $1.50 a pound. For the sake of variety on different jobs, occasionally substitute either the threaded or zinc-coated steel rod found in the hardware section of most lumber yards. Keep in mind, however, that zinc plating almost doubles a steel object’s detectability to a metal detector. Do not use zinc-coated rods where this would be a problem.

Use a hacksaw to cut the steel rods into three and four inch lengths. This allows you to fit the pin to different hole depths.

Saftey Glasses — Buy and wear simple plastic safety glasses that do not block your side vision.

Rags — Always have plenty of clean rags available to keep your equipment wiped free of fingerprints.

Caulk — Buy a standard caulk gun and tubes of clear silicon caulk (like GE’s Silicon II). This keeps it quick, clean, and cheap.


Pinning is best accomplished by a two-person team using the following five steps:

  1. Drill a hole at a slight downward angle in the tree. Your drill bit should be slightly larger in diameter than your steel pins.
  2. Use the caulk gun to squeeze clear silicon into the hole.
  3. Insert the steel pin. If the hole is more than 4 inches deep, use a 4 inch pin. If the wood in a particular spot is too tough, don’t force it. Use a 3 or even 2 inch pin in a shallower hole. Use another piece of steel rod, from 6 to 12 inches long, to push the pin to the bottom of the hole. Glue the pin in place with the silicon (otherwise a powerful magnet could pull it out).
  4. Place another dab of clear silicon at the mouth of the hole. This seals the hole against invasion by bugs or disease.
  5. Camouflage the opening with a chip of bark stuck onto the silicon.


Because of the relative silence of this technique, it can be used in sections of timber slated for immediate felling. You should not limit yourself to standing trees, however. Effective monkeywrenching involves examining every step in the processing of old-growth timber, from mountainside to mill door. Since metal detectors are often used to locate nails, old fence wire, and other scrap metal in logs before milling, observe this process from a safe distance to see if you can infiltrate the work area at night and insert your pins after the metal detection phase. If even greater silence is necessary, switch to a brace and bit (a crank-like hand drill available at all hardware stores). This entails more manual labor, but you don’t need to pin fifty logs. Six to a dozen will do quite well. Make sure you remove any telltale shavings or sawdust that can reveal your activities.

— T. O. Hellenbach

Field Notes

  • Jam a branch in a drilled hole after it is pinned. When the tree is debarked in the mill, it will not appear as suspicious as a plastic-filled hole would, and will merely appear to be a knot.
  • Normal drill bits are too short for old-growth trees. Use long ones.
  • Devise a system for keeping track of your tools in the dark — a fanny pack or a tool belt with holsters.
  • Instead of using a drill larger than the pin, try using one the same size and then driving the pin in. Driving the pin into a drilled hole requires much less force and noise than hammering into undrilled wood and still eliminates the need for caulking if you plug the hole with a wood dowel the same size as the pin and cut it off flush.

Other Pinning Techniques

Included here are three short articles detailing other monkeywrenchers’ refinements on the original tree pinning technique.

Super Pins

At least two kinds of steel pins available are two or three times more resistant to saw blades than is welding rod. They are Drill Rod and Dowel Pins.

1) Drill Rod. Most major steel companies sell this product (see your Yellow Pages under Metals). It’s round and comes in all the common drill diameters (one of its uses is as drill bits). It comes in three foot lengths and can be easily hacksawed into desired lengths. It possesses about the same soft mechanical characteristics as spikes and rebar — until heat treated. It then acquires the strength of the jaws of the bolt cutters that can be used to trim the heads off spikes!

Heat treating is not difficult. The best grade of drill rod steel to use is the water hardening variety designated grade W-1. Hardening requires only a propane torch, a cheap pair of needle-nosed pliers, and a container with at least 2 gallons of warm water. Cut a 7 inch length of drill rod. Hold one end with the pliers and heat the rod by playing the torch evenly up and down the pin. Soon it will begin to glow black-red. Continue heating until the pin glows cherry-red. Then drop (quench) it in the container of warm water. Don’t overheat the pin. After cherry-red, overheating begets red-orange, orange, orange-white, and white hot. Stop at cherry-red. You get but one chance and if you blow it, you can’t go back and start again because the metal goes through an irreversible phase change. If in doubt, check the finished pin with a file. Properly heated pins will be harder than good files.

When the pin has cooled, remove it from the water and wipe it dry. Be careful not to drop it. It is harder than Japanese trigonometry but as fragile as an icicle. It lacks toughness. Toughness is achieved through a process called tempering. Place the pin in your kitchen oven and bake (temper) for an hour at 525°F immediately after quenching. More than one pin can be tempered at a time.

Now you have a super pin.

A simpler alternative is:

2) Dowel Pins. These are used for aligning hunks of machinery, like the two halves of a Volkswagen engine. Dowel pins are sold in the common fractional diameters (see your Yellow Pages under Fasteners). Maximum lengths vary with the diameter. For example, 3/16 inch pins run to 2 inches long, 1 /4 inch to 2 1/2 inches, and 5/16 to 3 inches long.

These pins have been heat treated so that their interiors are very hard and their outer surfaces are super hard. For a given diameter, the shear strength of dowel pins is over three times that of rebar or welding rod.

Soft, stainless steel dowel pins are sold as well as a heat treated variety of stainless. Skip the stainless products. Insist on common alloy steel dowels. They’re the strongest and the least expensive.

Because drill rod and dowels are much stronger than other steel pins, they are effective tree spikes in smaller diameters. Therefore drilling holes for them requires less effort. Hand drilling holes for these pins can be done with an old-fashioned bit and brace. Twelve and eighteen inch long drill bits are available and “lean-against” braces make drilling easier. And drilling by hand is silent!

Placing pins deep in the tree by drilling farther into it is best. More expensive metal detectors are required to find deeply implanted pins, and the deeper the pin, the more difficult it is to remove it.

When using high strength pins instead of rebar or spikes, it’s the cross-sectional area that matters, not the diameter. Pins 3/16 inch in diameter are sufficient.

— Henry Bessemer

An Advanced Tree Pinning Technique

The government had the foresight to train me in demolitions and sabotage and it still dominates my thinking. After studying the tree problem we have come up with what we think is a sure fire way to neutralize the cutters. This method is an improvement over the already good tree spiking procedure in earlier editions of Ecodefense.

Wholesale tool companies (check the Yellow Pages for a major city) sell cordless electric drills’ with removable nicad battery pacs. These are the heavy industrial models made by Mankita and the like, not the cheap little things sold in Wal-Mart. Replacement battery pacs and chargers are available, and this is important. Tool companies also sell “aircraft extension bits,” which are very long drill bits, in lengths up to 18 inches.

Get some lengths of oil hardening tool steel rod (drill rod) of at least 1 /4 inch diameter. This is soft annealed steel that is usually worked into shape then made hard by heat treating. Cut the rod up into three to six inch pieces with a metal cutting band saw (or have it done in a machine shop). Have the short lengths of rod heat treated by a company that does that and tell them to draw the rod lengths back to Rockwell 49–50. This gives them aspring temper which is hard yet flexible.

Drill holes in trees, higher than eye level, with an extension bit 1/32 or 1/16 inch larger in diameter than the steel rod and slanting slightly downwards. The rods can then be inserted into the hole with adhesive and the hole filled with wood putty or ideally a plug of the same wood of which the tree is composed. A piece of bark glued over the hole will totally obscure the defect. The spare recharged battery pacs will allow an operator to drill quite a few holes, and probably work all night. The drills are fairly quiet, but I recommend silencing them with foam covers.

The best plan would be to inoculate as many trees as possible in a random pattern in any one section, concentrating on the areas of current cutting so they will run into a densely pinned area fairly quickly. Just in case sophisticated metal detectors can pick up the metal pins, load ceramic rods in a few holes or even tungsten carbide rods which are expensive but non-magnetic.

After giving the stand its shots, inform the processor’s insurance company of what was done and why. If no insurance company will cover them, they won’t cut.

If you can afford it, carbide rod is best because it is non-magnetic and absolutely no saw will get through it. Remember to buy carbide rod to length, since you can’t cut it without a special diamond wheel (you might check with a lapidary supply house for this kind of diamond wheel).

Of course, observe all security precautions when ordering material — especially by mail.

— Allen Dulles

An Increment Borer

The increment borer is a tool that almost every forester carries and uses on occasion. It is used to bore into the trunk of a tree in order to extract a core. (The core can tell a forester such things as the age and health of the tree.) The tools, made from Swedish steel, are anywhere from 4” to 30” long and come in three bore sizes (4, 5, and 12 mm). The 16 inch length retails for about $100 in the Ben Meadows Catalogue. Other forestry supply outfits also sell them. (Try Forestry Suppliers, Inc., POB 8397, Jackson, MS 39204–0397.)

Unlike spike and hammer, the increment borer is quiet, and bores a 1/4” to 5/16” hole which will take 6” of 1/4” round file. A round, or rat-tail file, makes an excellent pin — one far more resistant to a saw than a spike. Part of the core can be returned to cover the hole. The hole seals itself with pitch in a short time.

The borer and file, unlike a hammer and spikes, would be expected in the forest or on a timber sale area, especially if you are wearing an old Filson cruiser’s jacket and carrying a cruiser’s ax.

Proper use of an increment borer takes a little practice. While it can be rotated, it must never be bent, or it will splinter. Further, it is best to remove it immediately after the core has been extracted. Otherwise, the tree seems to set up on it after a while, making extraction difficult. If, in boring a tree, you inadvertently run into rot in the butt, it may be necessary to pull back with all your weight, while rotating the instrument in order to re-engage the threads in sound wood.

Of course, in case questioned, it pays to bone up on some forestry terms: mean annual increment, rings per inch, low site, high site, standard deviation, etc.

Yes, $100 is a lot of money for an individual to spend, but the reduction in court costs might make it worthwhile.

— Vecchio Silva

Field Note

Borer tools can be ordered from International Reforestation, Eugene, OR. 1-800-321-1037. 8” borers are $83.00 (plus postage); 10” borers are $97.50; 12” borers are $105. (Be extremely security-conscious when ordering by mail!)

A couple of things should be remembered when using borers: 1) To avoid getting it stuck in the tree, never leave the tool in the tree longer than absolutely necessary; 2) When removing the core, never force the spoon in or out if the core appears to be stuck. If you do, you may tweak the spoon out of shape, ruining it. Instead, repeat the release procedure. If the spoon won’t come out with the borer in the tree, back the borer all the way out before removing the core.

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