A fastenable device includes a housing having a base portion, a head portion opposite to the base portion, and a body portion between the base portion and the head portion. The base portion has a first fastener in the form of a full ring integral to the housing and defining a through-hole. The head portion has a second fastener in the form of an open ring integral to the housing and defining a snappable recess. The device includes a frequency generator housed in the housing and electrically connected to an electrode pair disposed on the housing, for applying a voltage with at least two different frequencies between the electrodes.
