Plain candle moulds are used for making cylindrical or pillar-shaped candles. These moulds come in various sizes and are made from metal. To use them, first, melt the candle wax and add any desired colours or fragrances. Then, place a wick in the center of the mould and pour the melted wax into the mould, making sure to leave a small amount of space at the top. Once the wax has solidified, remove the candle from the mould by gently pulling the sides away from the wax. Trim the wick to the desired length, and the plain candle is ready to use or decorate as desired.