Metate y Mano (Mortar and Ground Stone) . The traditional Aztec metate is slanted and has short legs; it is made of volcanic rock, basalt or andesite. The slant in the metate allows the grinder to push the ingredients as they are being ground into a bowl set at the end of it. The mano is the long cylindrical stone roller, with which substances are ground and rolled with. Just sit or squat in front of the metate, then scatter grain in the metate, and then roll the mano across the metate back and forth. This back and forth motion pulverizes grains, seeds, or chocolate in an even, smooth and efficient way. The use of the metate has made women develop strong upper backs and arms. How to Prepare or Season your Metate and Mano before use: Make sure to season your metate before using so there will be no grit in your food. 1. Douse your metate and mano and scrub with a stiff brush. Soak overnight and then let dry for a day. 2. Once the metate is dry, grind a handful of white rich rice, pulverize until the rice turns into grey powder. Discard the gray powder. Grind another handful of rice, and continue grinding until the pulverized fine powder produced is white, which means the loose sand or stones have been removed from your metate. 3. If you are going to use the metate to grind spices, then just follow the rice procedure. If you are grinding corn, then substitute the rice for corn and discard the first batch.