The simplest hitch

[xarax]

   The least simple thing in any "simple" thing, is the very notion of "simplicity" itself  - and a "simple knot" is no exception to that (1). Nevertheless, few knot tyers would argue that the simplest noose is the one where, in order to join the returning eye leg and the Standing End, all we have to do is to tie a simple overhand knot with the former, around the later ( ABoK#1114 ). It turns out that this noose is not very safe, so it is recommended that we further secure the Tail End by tying a second, additional overhand knot on it, as a stopper.
   However, there is yet another noose, as simple as this, which is not only much safer ( so it does not require the tying of this second overhand knot, or of any other stopper, on its Tail End ), but it can also be used as a tight hitch. ( A tight hitch is a hitch which, once clinched around the object, it remains tightly attached on it, because both its ends, the Tail End AND the Standing End as well, are somehow "locked", and can not slip through the knot, even when the Standing End is not being pulled any more. Therefore a tight hitch can also be used as a binder (2)).
   What can be as simple as the overhand knot tied on the returning eye leg of the Simple noose ( ABoK#1114) ? An underhand knot !    If, instead of using an overhand knot in order to attach the returning eye leg on the Standing End, we use an underhand knot, we tie the noose I had called the "Simplest hitch" - because it can be used as a hitch, and a rather tight one. In contrast to an overhand knot, the underhand knot, being squeezed on the surface of the object, closes very tightly around itself, it almost jams, so the penetrating Standing End can be "locked" and immobilized very efficiently ( See the attached picture ).
   It is easy to distinguish the Simplest noose ( ABoK#1114) from the Simplest hitch at a glance : When we use an overhand knot, the Tail End is oriented towards us - when we use an underhand knot, the Tail End is oriented towards the hitched object.
   There are many cases where the mere substitution of an overhand knot by an underhand knot has noticeable results, but the difference here is spectacular, indeed : One has only to tie those two simple nooses around a pole, and then pull them snug. As we pull their Standing Ends, the overhand knot becomes even looser, and allows its Standing End slip through, while the underhand knot becomes even tighter, and "locks" its Standing End.

1.  http://igkt.net/sm/index.php?topic=3740.0
2.  http://igkt.net/sm/index.php?topic=4673.0

P.S. Some people call "overhand knot" what I use to call "underhand knot", and vice versa. The names / labels we prefer do not matter : if the Simplest Noose ( ABoK#1114) is tied by the one of those mirror-symmetric knots, the Simplest hitch is tied by the other. See the last picture, taken from :
https://www.gutenberg.org/files/13510/13510-h/13510-h.htm
Knots, Splices and Rope Work, by A. Hyatt Verrill

[Sweeney]

It's interesting the way this works as a hitch when it does hold tightly. I like the bowstring knot as a simple noose (though no use as a hitch) - in particular because the noose gets bigger if it does slip so I used it to make a temporary collar and lead for a dog. A friend of mine was having trouble taking a stray back to its owner a couple of weeks ago - there is no danger of the dog being choked should the noose slip.

Barry

[Dan_Lehman]

there is yet another noose, as simple as this, which is not only much safer ...

Indeed, and I was surprised not to find such a simple
knot in ABoK.  It's one that I myself often use.

But one does need some care to ensure that the tail gets
properly drawn by the SPart and nipped (but seems to
work more surely in this than if the overhand is in
the opposite orientation!).  For this reason, working with
a slightly more complex knot such as #525 (what I like
to call the "symmetric fig.9") can give a safer option.
There are various ways for this knot to be arranged qua
noose --play around with it.

The OP's structure is #525, if one removes the object!


--dl*
====

[xarax]

...one does need some care to ensure that the tail gets properly drawn by the SPart and nipped

   True. The important thing one has to remember, is that the Tail End should remain parallel to the Standing Part = direct continuation of the Standing End ( see the attached pictures ).
   
   At the tight knot, when, as a consequence of the removal of any slack in the wrap, the nub is pulled towards the hitched object and is forced to be squeezed on its surface, the Tail End is pushed to the one or to the other side of the Standing Part. Personally, I prefer the configuration shown in the pictures : in that, the first curve on the continuation of the returning eye leg meets the Standing End before the Tail End ( and at the optimum, the "right" angle ), and this ensures a more efficient "locking" of it. In this particular knot, it is the Standing End which should better absorb the greater portion of the tension running along the returning eye leg, and should be "locked" by it as efficiently as possible, because the Tail End, as part of the underhand knot, is already sufficiently secured. Moreover, as a bonus, in this configuration the last curve of the Tail End is more "natural" = wider, which is an advantage when the knot is tied on stiff ropes. However, I have seen that the other configuration, where the Tail End lies at the other side of the Standing Part, can also lead to tightly woven nubs and stable, tight hitches. (*)

   P.S.
   One may imagine that if, instead of the underhand knot, we tie a double underhand knot, the resulting "longer" nipping nub would be able to "lock" the penetrating Standing Part more efficiently. Noope !    On the contrary, the Standing Part becomes able to slide on its larger contact area with the two turns of the double underhand knot, and slip through them more easily. What immobilizes the Standing Part is the part of the first curve of the returning eye leg, which meets and "bites" it at the optimum angle ( the "right" angle ), and thus increases the applied friction forces - NOT the contact area of the encircling turns.   

(*) However, in this "other" configuration, the Tail End after its last turn, and the Standing End, are not perpendicular to each other at their point of contact, as in the original Simplest hitch, shown in the pictures - therefore the Tail End can not "bite" the Standing End in the most efficient manner ( remember, the "right", optimum angle, for lines to "bite" deeper in each other s body, and not slide on each other s surface, is the right angle, 90 degrees ), so in this "other" form of the Simplest hitch the Standing End, going through the underhand knot, can not be "locked" and immobilized as securely as in the original form. To this day, I have not found any "Jam knot" ( Ashley s term, explained at ABoK#1228 ) simpler and/or tighter than the original form of the Simplest hitch. Even if the more convoluted/complex Buntline hitch ( which is probably the best of the well known "Jam knots" ) is pre-tensioned as much as possible very tightly ( by pulling hard both ends, the one after the other, many times ), the Standing End can not be "locked" very effectively, so the hitch can not become ( and remain so, when it is not loaded ) very tightly wrapped around the encircled object(s).         

[xarax]

   It is easy to distinguish the Simplest noose ( ABoK#1114) from the Simplest hitch at a glance : When we use an overhand knot, the Tail End is oriented towards us - when we use an underhand knot, the Tail End is oriented towards the hitched object.

   I understand that many people have a difficulty to distinguish an overhand knot from an underhand knot, because those two knots are mirror symmetric to each other, and mirror symmetry may be confusing.
   So, the following is another method to distinguish the Simplest noose ( ABoK#1114 ) from the Simplest hitch : When, just after we make the eye of the noose, or the round turn of the hitch, we first pass the Working End through the eye, or through the "triangle" formed by the Standing End, the returning eye leg and the hitched object, and only after this we retrace the path of the Standing Part to tie the nub, the Working End which now becomes the Tail End is oriented towards the object, so we tie an underhand knot, and the Simplest hitch. If, on the contrary, we do what may seem "easier" and so it is commonly done, we first pass the Working out of the eye, or out of this "triangle", and only after this we retrace the path of the Standing End to tie the nub, the Working End which now becomes the Tail End is oriented towards us, so we tie an "overhand knot", and the Simplest noose ( ABoK#1114 ). 

[Dan_Lehman]

   P.S.
   One may imagine that if, instead of the underhand knot, we tie a double underhand knot, the resulting "longer" nipping nub would be able to "lock" the penetrating Standing Part more efficiently. Noope !    On the contrary, the Standing Part becomes able to slide on its larger contact area with the two turns of the double underhand knot, and slip through them more easily. What immobilizes the Standing Part is the part of the first curve of the returning eye leg, which meets and "bites" it at the optimum angle ( the "right" angle ), and thus increases the applied friction forces - NOT the contact area of the encircling turns.

One can wonder what you mean by the highlighted knot
name --as there are various geometries that can apply.
IMO, making an anchor bend orientation, and one that
is opposite to the OP --i.e., tail will point away from the
object--, will give a decent nipping grip, and more so if the
structure is revised to be a sort of minimal ProhGrip hitch
(aka "Blake's H.").  I favor this orientation as the noose's SPart
is first entering the knot at a lesser-stressed point, not where
the knot-SPart (to distinguish from the noose-SPart) turns.

--dl*
====

[xarax]

a double underhand knot,

One can wonder what you mean by the highlighted knot name --as there are various geometries that can apply. IMO,

  Mea culpa. I should had posted the picture below right away.
  Tying an underhand knot, if you encircle the continuation of the Standing End of the hitch one more time, that is, if you form a two-turn coil, you tie the shown knot which I had called, without much justification, a "double underhand knot". As you correctly point out, there are various geometries which can be described by the same name...
   
   My general theory, which is corroborated by my experience + my trials ( but NOT any decent tests ! ! ! ), is that, contrary to the common conception, a double-turn nipping structure / "nipping tube", does not nip a penetrating segment more efficiently than a single-turn one. If you wish to bite deep and hard, you may simply increase the force with which you bite - however, if you can not do this, if you have already exhausted any available source of additional force, you better bite with one tooth - two teeth present a larger area of contact, but they do not sink into the body of the bitten elastic and compressible material ( as the material of a rope is ) to the same depth. On the contrary, the more extended area of contact presents a necessarily smoother surface, with shorter crests and shallower troughs, where the segment which we wish to bite can slide more easily. To immobilize a segment of a rope being pulled towards one direction, it is better to use the least number of other segments placed perpendicularly to this direction, which, when squeezed towards the surface of the to-be-immobilized segment, will bite it harder and deeper. More than one segments will offer increased safety regarding the long-term accumulated wear of the ropes on the areas of mutual contact, that is true, but not additional safety regarding slippage.
   

[Ruby]

seems that only parallel is not enough. in the first pic the tail is in the right. if the tail is brought to left, still parallel, then the knot would slip like granny knot.

anyway it's only a jammed overhand, almost impossible to untie.

[xarax]

if the tail is brought to left, still parallel, then the knot would slip like granny knot.

   No. If you hold the nub by the one hand on the surface of the pole, and you pull the Standing End with the other, ( as I had described elsewhere ) it, too, becomes tight and secure. However, I prefer the "tail to the right", as you describe it, because that was the whole idea of the knot right from the start : I tried to apply the idea of the "opposing bights locking mechanism", by forming the two bights by the same line, the one after the other !
   Regarding the "to the left" or "to the right" issue, read the note (*) at the end of Reply#3 - what matters more is not the tail going "right" or left", but "under". 

 

  it's only a jammed overhand, almost impossible to untie.

   If the overhand noose is the overhand noose ( ABoK#1114 - which, mind you, is NOT "only an overhand"(sic)  ...), this is the underhand noose. And, as I had said time and again, for a one-wrap hitch, it is a good thing if it manages to become jammed !