An increment borer is the least invasive way to count tree rings and takes a small (0.200 inch diameter) straw-like sample from the bark to the pith of the tree. Though this hole is small, it can still introduce decay in the trunk. To prevent this, trees are limited to one bore every six years and the core is reinserted into the core hole.
The increment borer is made of carbide steel which makes it a relatively expensive tool. The borer has three parts; the handle, the steel shaft and the extractor. Proper maintenance and operation are essential if the tool is to last. Borers come in different sizes and should be at least 75% the diameter of the tree you are boring. Keeping the borer sharp is very important for taking quality samples and cores.