|This article is about an older version of DF.|
Mechanisms are created by a mechanic at a mechanic's workshop out of a stone. They can also be forged from 3 adamantine wafers at a Forge. Building traps, levers, pressure plates, and gear assemblies requires one mechanism. Linking objects to a lever or pressure plate requires two mechanisms per linked item (one for the object, one for the lever). If you want to ever recover those mechanisms you need to deconstruct both the linked object and the lever.
It is a mechanic's job to install mechanisms. Mechanisms can be linked to objects at any distance.
Mechanisms make surprisingly good trade items, due to their high base value of 30, but are heavy compared to crafts and so may not be a good trade good if wagons can't access your trade depot. Since their value is higher than that of a statue, levers and gear assemblies make good alternative room decorations.
Since mechanisms count as furniture, the jeweler's workshop action encrust furniture with [gem] can encrust mechanisms with gems instead of actual furniture.
High-quality mechanisms improve the accuracy of weapon traps, as stated by Toady here. This means weapon traps will benefit more from high-quality mechanisms.
A mechanism's quality has no effect on how quickly it operates.
The only stones that can withstand the heat of magma are bauxite and raw adamantine, so make bauxite mechanisms if you plan on using floodgates to hold back magma and don't want to use your precious adamantine for such a task.
NOTE: Even if your floodgate and floodgate's mechanism are both made of magma-safe materials (such as bauxite), if you link even a single additional lever to the floodgate using a non-magma-safe mechanism, you will have a very unpleasant last-minute surprise. When linking a trigger to an object, the first mechanism selected is attached to the object, the second is attached to the trigger. Unless the trigger itself will be submerged in magma, only the first, the one attached to the object (that will be submerged) need be of bauxite.
In this version, the only metal that can be used for making mechanisms is adamantine, though the availability of bauxite generally makes this largely unnecessary. As an alternative, if one is not averse to a little modding, adding the [ANY_USE] flag to a metal such as iron will give it the same properties as adamantine for forging purposes, including the ability to make mechanisms from that metal at any forge. Subsequent versions (0.31 and later) permit making mechanisms from other types of metal.