Playing with the TackleClamp hitches and their lighter, simpler variations presented in this thread, I came upon the variation of the Double Cow hitch shown in the attached pictures. It is not as secure a knot as the original Double Cow hitch, but it has a great advantage : It can be released instantly, without any manipulation of its two ends. Moreover, to release it, we have only to use three fingers of one hand, and a minimum of force. The tied and pre-tensioned hitch can can be released very quickly and easily, indeed, even if/while its round turns are tensioned to a high degree. This is due to the fact that, as both ends pass through the same opposed bights, the final, outer bight can be pushed out of its grip around the two ends, and release the whole knot at a glance. ( I am afraid I can not explain it in a more precise way - one has to tie the knot, tighten it as hard as he can by pulling both ends against the pole, and then release it by pushing this last/outer bight, to see what I mean.)
Of course, like the single and double Cow hitches, this hitch can be tied in the bight, and used in place of the Pile hitch, for example. It can be described as an elongated Cow hitch, where the the bight that connects the two ends in the common Cow hitch makes two more turns around the pole - so the ends pass through three bights, the last one ( the " trigger" of the release mechanism...) being opposed to the other two. I call it quick/easy release (QER) Double Cow (hitch), but I can change this label if it reminds anything else...
When I first tied this hitch, I dismissed it, because I thought that the "trigger", the last/outer bight, could easily slip over the two ends. Yes, it can, but not by itself ! It needs a light, intended, directional push- so this seemingly weak point is a hidden advantage : this hitch can serve in applications where we need a tight grip, able to withstand lengthwise pull, but we also need a hitch that can be released quickly and easily.