The Barktax bark gauge consists of a shaft with a sharp point which is pushed through the bark until the underlying wood is felt.

The sleeve around the shaft is shifted to the surface and the thickness of the bark sample can be read from the calibrated shaft. The gauge is in aluminum with a durable plastic end knob/handle, and has a graduation available as either millimeter or inch.

Bark thickness and texture vary greatly between different tree species. The bark can be everything from several centimeters thick, to just a fine layer. To perform a measurement of stem diameter over bark can be difficult and can show significantly greater values than of the wood below bark. It is important to know just how thick the layer of bark is on the tree or log.