The concept of using a collar or large cylindrical object to increase shear strength in wood construction has been around for several centuries in the forms of split rings and shear plates.[11] Shear plates provide a larger load-carrying capacity in shear than can be otherwise achieved by a bolt alone.[12] Because this idea utilized less bolts for equal strength, it transferred well into the use of live trees, as they compartmentalize more efficiently with a single, larger cut than several, smaller cuts.[13] Michael Garnier became involved in treehouse construction[4][14] beginning in 1990 when he built his first treehouse in Josephine County, Oregon. Two years later, he was ordered by County official to close the treehouse to the public. He began developing what would become the Garnier limb, a high-strength alloy steel engineered bolt that can be screwed into a bore in the trunk of tree. In 1997 Garnier met Arborist Scott D. Baker who shared his knowledge of tree biology and tree structural responses. By 1998, Garnier had developed a commercial bolt product which he called Artificial Limbs. The Garnier limb was primarily developed to satisfy the safety requirements of the Josephine County Building and Safety building permit process.[15][16]
Engineer Charley Greenwood, with the help of Michael Garnier and machinist Michael Birmingham, added a 3-inch (76 mm) collar onto a 1.25-inch (32 mm) hex cap screw to maximize the surface area and minimize compression in the contact area between the tree and the screw.[17] Garnier was initially the sole producer of these bolts under the names, “Artificial Limbs” and “Garnier Limb”.[16]
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