Basal anchor examples
Many other basal anchor variations are possible - below are provided as examples only .
Belay device set on sling ; sling tied off by girth hitching around trunk
! Stopper knot ( marlinspike hitch with karabiner ) installed 80cm below belay device according to Petzl instructions .
! System can be lowered if rescuer injured or as part of rescue plan .
! Sufficient tail of rope must remain below device to lower system to ground - ropejoining knots will not pass device .
! Sling must cinch tight around base of tree . Take care with anchor sling attachments that do not cinch ( e . g . Wrap 3 Pull 2 ): on smooth-barked trees with pronounced root flare these may slip if loaded vertically .
Rope tied off with round turn and two half hitches
A common way to rig for rescue is to secure the rope directly around the tree using a knot which can be untied under tension .
! If necessary , knot can be untied under tension , and the turn around the tree used as friction to lower the rescuer . This system is not fail-to-safe and a suitable backup must be installed before relying on the friction .
! Additional rope can be joined if necessary - knots will pass trunk .
! If the knot is tied using a bight then additional rope can be joined before untying this connection .
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