Mechanical training dummy[1] is a placeable construction for training the combat skill of dwarfs assigned as warriors. It's more efficient than the simple training dummy.
Bug: A Wooden Shield had mistakenly replaced the Skull Shield in the crafting recipe. Since there are no shields in the base game, the Mechanical Training Dummy could not be crafted without the Sisters in Arms DLC: it would appear in the inventory menu with an empty recipe and a disabled craft button; and the item itself would disappear from the craft tree.[2]