Isolating a target branch
Many climbers attach a weight to both ends of their throwline . This allows the line to be ‘ manipulated ’ into a target fork , by alternating between pulling up each side of the line so that both sides drop down parallel and the target union is isolated .
An alternative , where the line passes through tight forks or you are unsure that you will be able to isolate the union , is to use the double bagging technique .
A The line is fired or thrown through multiple unions of the tree .
The line is allowed to run to the ground , where a second throwline and throwbag are attached to the original throwbag .
B
The original line ( shown in red in the pictures above ) is pulled back until both bags are hanging between the two unions .
C Both lines are allowed to run to the ground .
D
The lines are separated on the ground . Note that in the pictures above , the technique could have been used to isolate either of the unions through which the original line passed .
Note that the same technique can be used even if the original line did not pass through any suitable forks . In the image on the right , a thin , unsuitable branch has been used as a ‘ craning fork ’ to lift a second throwline up and over a suitable union .
This is an excellent technique for isolating branches in a dense or crowded tree - simply fire a line over the whole canopy , drop the bag down through the structure , and use this technique to isolate a single chosen union .
It is important to note that isolating the branch will not always be necessary . Where a climbing line is to be tied off with a basal anchor , and where every union it passes over is of sufficient strength , the line can be set without isolation .
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