One of the biggest concerns for woodworkers when planing timber is encountering contamination in the wood that can damage high speed planing knives. A Lumber Wizard Metal detector has a finely wound field of copper wire inside the "head" of the unit that has electricity passing through it continuously, creating a Magnetic Field. When metal is encountered in this testing field, it changes the stability of the field which the electronic circuit recognises and several alarm functions are tripped viz. warning light, buzzer, handle vibration and in the latest Model #4, a laser flash line.