Tin foil hat radio with a metal bucket. The AM radio is completely inside a metal enclosure. This leads to a noticeable reduction in signal strength received by the AM radio. The efficiency of a metal enclosure in blocking electromagnetic radiation depends on the thickness of the foil, as dictated by the "skin depth" of the conductor for a particular wave frequency range of the radiation. For half-millimetre-thick aluminum foil, radiation above about 20 kHz (i.e., including both AM and FM bands) would be partially blocked, although aluminum foil is not sold in this thickness, so numerous layers of foil would be required
Foil (fencing) Foil (fencing) A foil is one of the three weapons used in the sport of fencing, all of which are metal. It is flexible, rectangular in cross section, and weighs under a pound. As with the épée, points are only scored by contact with the tip, which, in electrically scored tournaments, is capped with a spring-loaded button to signal a touch. A foil fencer's uniform features the lamé (a vest, electrically wired to record hits in such cases), a jacket (made of strong cloth covering the groin area, chest and arms), a glove, so called knickers (in the US or