A tool is any physical item that can be used to achieve a goal, especially if the item isn't consumed in the process. Tool use by humans dates back millions of years, and additional animals are additionally known to employ simple tools.

Tools that are used in particular fields or activities might have different designations such as "instrument", "utensil", "implement", "machine", "device," or "apparatus". The set of tools needed to achieve a goal is "equipment". The knowledge of constructing, obtaining and using tools is technology.

History

Prehistoric stone tools over 10,000 years old, found in Les Combarelles cave, France
Carpentry tools recovered from the wreck of a 16th-century sailing ship, the Mary Rose. From the top, a mallet, brace, plane, handle of a T-auger, handle of a gimlet, possible handle of a hammer, and rule.
Stone and metal knives

Anthropologists believe that the use of tools was an important step in the evolution of mankind. Because tools are used extensively by both humans and wild chimpanzees, it is widely assumed that the first routine use of tools took place prior to the divergence between the two species. These early tools, however, were likely made of perishable materials such as sticks, or consisted of unmodified stones that can't be distinguished from additional stones as tools.

Stone artefacts only date back to about 2.5 million years ago. Notwithstanding a 2010 study suggests the hominin species Australopithecus afarensis ate meat by carving animal carcasses with stone implements. This finding pushes back the earliest known use of stone tools among hominins to about 3.4 million years ago.

Finds of actual tools date back at least 2.6 million years in Ethiopia. One of the earliest distinguishable stone tool forms is the hand axe.

Up until recently, weapons found in digs were the only tools of “early man” that were studied and given importance. Now, more tools are recognised as culturally and historically relevant. As well as hunting, additional activities required tools such as preparing food, “…nutting, leatherworking, grain harvesting and woodworking…” Included in this group are “flake stone tools".

Tools are the most important items that the ancient humans used to climb to the top of the food chain; by inventing tools, they were able to achieve tasks that human bodies could not, such as using a spear or bow and arrow to kill prey, after their teeth weren't sharp enough to pierce a large number of animals' skins. “Man the hunter” as the catalyst for Hominin change has been questioned. Based on marks on the bones at archaeological sites, it is now more evident that pre-humans were scavenging off of additional predators' carcasses rather than killing their own food.

Mechanical devices experienced a major expansion in their use in Ancient Greece and Ancient Rome with the systematic employment of new energy sources, especially waterwheels. Their use expanded through the Dark Ages with the addition of windmills.

Machine tools occasioned a surge in producing new tools in the industrial revolution. Advocates of nanotechnology expect a similar surge as tools become microscopic in size.

Functions

One can classify tools according to their basic functions:

Some tools might be combinations of additional tools. An alarm-clock is for example a combination of a measuring tool (the clock) and a perception tool (the alarm). This enables the alarm-clock to be a tool that falls outside of all the categories mentioned above.

There is a few debate on whether to consider protective gear items as tools, because they don't directly help perform work, just protect the worker like ordinary clothing. They do meet the general definition of tools and in a large number of cases are necessary for the completion of the work. Personal protective equipment includes such items as gloves, safety glasses, ear defenders and biohazard suits.

Tool substitution

Often, by design or coincidence, a tool might share key functional attributes with one or more additional tools. In this case, a few tools can substitute for additional tools, either as a makeshift solution or as a matter of practical efficiency. "One tool does it all" is a motto of a few importance for workers who can't practically carry every specialised tool to the location of every work task; such as a carpenter who doesn't necessarily work in a shop all day and needs to do jobs in a customer's house. Tool substitution might be divided broadly into two classes: substitution "by-design", or "multi-purpose" , and substitution as makeshift. Substitution "by-design" would be tools that are designed specifically to achieve multiple tasks using only that one tool.

Substitution as makeshift is when human ingenuity comes into play and a tool is used for its unintended purpose such as a mechanic using a long screw driver to separate a cars control arm from a ball joint instead of using a tuning fork. In a large number of cases, the designed secondary functions of tools aren't widely known. As an example of the former, a large number of wood-cutting hand saws integrate a carpenter's square by incorporating a specially shaped handle that allows 90° and 45° angles to be marked by aligning the appropriate part of the handle with an edge and scribing along the back edge of the saw. The latter is illustrated by the saying "All tools can be used as hammers." Nearly all tools can be used to function as a hammer, even though quite few tools are intentionally designed for it and even fewer work as well as the original.

Tools are additionally often used to substitute for a large number of mechanical apparatuses, especially in older mechanical devices. In a large number of cases a cheap tool can be used to occupy the place of a missing mechanical part. A window roller in a car could easily be replaced with a pair of vise-grips or regular pliers. A transmission shifter or ignition switch would be able to be replaced with a screw-driver. Again, these would be considered tools that are being used for their unintended purposes, substitution as makeshift. Tools such as a rotary tool would be considered the substitution "by-design", or "multi-purpose". This class of tools allows the use of one tool that has at least two different capabilities. "Multi-purpose" tools are basically multiple tools in one device/tool. Tools such as this are often power tools that come with a large number of different attachments like a rotary tool does, so you could say that a power drill is a "multi-purpose" tool because you can do more than just one thing with a power drill.

Multi-use tools

Bicycle multi-tool

A multi-tool is a hand tool that incorporates several tools into a single, portable device; the Swiss army knife represents one of the earliest examples. Other tools have a primary purpose but additionally incorporate additional functionality - for example, lineman's pliers incorporate a gripper and cutter, and are often used as a hammer; and a few hand saws incorporate a carpenter's square in the right-angle between the blade's dull edge and the saw's handle. This would additionally be the category in which the "multi-purpose" tools after they're additionally multiple tools in one (multi-use and multi-purpose can be used interchangeably). These types of tools were specifically made to catch the eye of a large number of different craftsman who travelled to do their work. To these workers these types of tools were revolutionary because they were one tool or one device that could do several different things. With this new revolution of tools the travelling craftsman wouldn't have to carry so a large number of tools with them to job sites, being that their space would be limited to the vehicle they were driving. The problem of having to deal with so a large number of different tools was solved with the overtaking of multi-use tools.

Use by additional animals

A Bonobo at the San Diego Zoo "fishing" for termites

Observation has confirmed that a number of species can use tools including monkeys, apes, elephants, several birds, and sea otters. Philosophers originally thought that only humans had the ability to make tools, until zoologists observed birds and monkeys making tools. Now the unique relationship of humans with tools is considered to be that we're the only species that uses tools to make other tools.

Tool metaphors

A telephone is a communication tool that interfaces between two people engaged in conversation at one level. It additionally interfaces between each user and the communication network at another level. It is in the domain of media and communications technology that a counter-intuitive aspect of our relationships with our tools first began to gain popular recognition. Marshall McLuhan famously said "We shape our tools. And then our tools shape us." McLuhan was referring to the fact that our social practises co-evolve with our use of new tools and the refinements we make to existing tools.