The windmill in the Slovene Hills typically has four blades, and in Haloze six blades, driving an axis with a sail or vane that is constructed to swivel so it is always positioned perpendicular to the wind. As the axis rotates, wooden hammers are lifted off their resting position by fixed notches. As they fall back, they rhythmically impact on a wooden board. While the quality of the sound is dependent on the wood of which the hammers and sounding boards are made, the rattle frequency depends on the number of hammers, as well as changes in wind speed.