the Midshipmans hitch (or tautline hitch)
This is a remarkably useful knot. It is adjustable AND trustworthy.
Each sailor should know how to tye this knot in any circumstance. Especially to tye himself to a rescue rope thrown to him in the water. On the lifeline he has to hold the loose end securely to the standing part. This gives a good grip and a useful goal in this critical situation (HOLD!)
Anyone who uses a tent should know this knot. It is the best way to adjust your lines to the tent-poles. It is the most simple of the adjustable knot family.
A short video:
the Adjustable hitch (or Jamming hitch)
This brother of the midshipmans Hitch is just a bit less important. This is because it tends to jam.
When jamming is desirable, this knot is o.k., as when work will be left unattended. Ashley states it was used by cotton brokers in New Bedford to tye their cotton samples they took from mill to mill. The packages could be opened and closed at will, and still be secure when left alone at travel.
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