Good answer from
Macro who thus earns all our consideration!
There are similar devices, like the one you are showing, but the one I have shown here seems simpler and more practical.
Its use allows to gently dismantle branches which, if they fell freely, could cause damage to nearby infrastructure. It allows several variants of descent while ensuring a role of blocking and especially of brake. As seen in the video below, shot by its inventor.
Another use, not considered by the latter, makes it particularly interesting: it allows the retention of a tree during felling by fixing it to another, this to ensure the hit in the case of trees that do not require Too much traction to go to the desired side: once the tree is correctly cut, it suffices to pull perpendicularly on the stretched rope to exert a very amplified traction ... This makes it possible to do without a winch in many cases and also constitutes A great time saver