Engineering:Fourth hand (tool)
From HandWiki
A fourth hand is the name of a specialized bicycle tool for manipulating brake and derailleur cables. The fourth hand allows a mechanic to keep the cable in place while they adjust the tension. Generally the fourth hand contains a locking mechanism.
The fourth hand is sometimes called a "cable puller" or "cable stretcher." Modern fourth hands are an improvement on an earlier generation of cable stretchers known as "third hands," hence the name.
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