In technical writing, a mechanism is defined as anything from an object to a device to a procedure. Technical descriptions of a mechanism may be a general overview of the mechanism, instructions on how to use the mechanism, or instructions on how to assemble the mechanism. Depending on the requirements and the mechanism being described, descriptions fall into one of two categories: general and specific.
A general description begins with an overview of the mechanism. Depending on the mechanism, this includes a physical description, list of parts, a stated purpose and the general function of the mechanism. An overview may also include instructions and a statement of which users the mechanism is designed to accommodate. A specific description of a mechanism includes the same kind of information, but more detailed information is included as well, such as other parts or procedures that are related to the mechanism.
A technical description of a mechanism is written in one of several ways. First, the description can be written in spatial order. This kind of description is ordered according to how the user views the mechanism: left to right or top to bottom. A functional order is when the description is written according to the order in which the mechanism will be used by an operator. Finally, chronological order is used to describe the order in which a mechanism is eventually disassembled or assembled.