The resistograph is an instrument that measures the energy expended by a needle penetrating a wooden element at a constant speed, with the resistance that the element offers to the penetration.

This test is a method of evaluating areas of wooden elements that exhibit degradation, rot or internal cavities. 

Resistograph readings allow us to estimate some mechanical characteristics of the wood, assess the conservation status of the structural elements and define what sections are still useful.

The results obtained have a simple interpretation and provide qualitative information of great interest, since they provide a drawn record of the variation of the resistance of wood to drilling.

The fact that it performs almost imperceptible perforations, and without any influence on the mechanical strength of the workpiece makes it one of the most used instruments in the inspection of timber structures.