SafeBloc is a triple hole thimble spliced onto a 3-5 ft. Tenex whoppie sling that adds friction in the rigging system to the top of the tree, thus adding safety by reducing rigging point stress, compared to a system that uses a block or pulley.
Use the SafeBloc sling anywhere you'd use an arborist block for lowering. The rigging line can be woven through the three holes for its maximum friction, or fewer holes for less friction.