The lever arm (a) in general is the distance from the point of application of the mass (m) to the pivot point / anchor point of the component. The load (F) increases linearly with the distance to the point of application of the load: F = m × a
Here is a simple example:
Extend your arm sideways and your partner presses with the same force from above, once at your elbow and once at your hand. The further out the force is applied (greater lever arm), the greater the load (torque) on your shoulder.
Transferred to the connection Tree – GTS Screw:
The lever arm is the distance from the tree trunk (bark) to the load application point (support & beam). The further the beam slides outwards on the shaft of the GTS, the greater the lever arm, the greater the torque and thus the load on the tree-screw connection.
If, for example, the Tree-GTS connection can withstand a load of 4 tonnes with a 10 cm lever arm, it would only be 2 tonnes with a 20 cm lever arm!
The pivot point of the GTS Tree Screws is in the inner third of the coarse thread.