The crystal wrench is used to configure the routing of essence between Ars Magica machines. Machines are connected by clicking and holding the crystal wrench between the two machines. If a machine or nexus is simply clicked, a beam of essence will shoot upwards. This represents the machine being put into a "link mode". Only certain machines can go into link mode.
The crystal wrench can be used to link essence nodes together. Start with the source (either a Mana Battery, an Essence Conduit, or a Nexus). It will go into link mode and a beam will shoot up from it. Then, right click the destination node (any block that can request or transmit essence...basically anything other than a nexus). If the nodes are close enough together (10 blocks distance max), they will be linked.
Note that if you link nodes with two different essence types, the destination node's essence type will be overridden, and it will lose any stored essence of the original type.
And thems facts.
Place the components in the following configuration: