A vertical shaft mortar mixer manufactured in Italy for the last 15 years, has been assembled and sold in the U.S. for the past four years. In their basic design, vertical shaft mixers are similar to the pan mixers used to make concrete in block plants. But these units come electric- or gas-powered and are towable for jobsite use. Their most striking feature is a vertical drum with a rotating vertical shaft at its center. In the largest model, two "tridents," one at each end of a revolving arm, spin freely as they are pulled through the mix. These tridents act like unpowered egg beaters. Each one has three small paddles, hence their name. Vertical shaft mixers are being used to make masonry mortar, stucco, and dry pack mortar for anchoring stone. Because it mixes materials dry, it can blend powdered color pigments with cement and sand before water is added. It can also make soupy high-strength grout, as long as the mix does not contain large aggregate.