Tunnelling is the process of building wormholes between two distant parts of space. This requires a ship with an ambi-powered interspatial bore that can punch through the sublayer in order to create the tunnel.
There are different ways to create a tunnel. One is with an anchored punch, using a series of pre-existing tunnels to get from point A to point B, and then connecting those directly to each other. This is a roundabout method, but relatively safe. Another is by doing a blind punch, which requires punching out of the sublayer without any form of infrastructure to help navigate. This method is much more dangerous, as it risks tearing the fabric of space. Tunnelling ships, such as the Wayfarer, need a separate license to do blind punches, and are legally required to have a Navigator on board.
Tunnelling jobs are classed into three levels, with Level Three being the smallest tunnels and Level One the largest. The bores for larger tunnels are more expensive, and can only be afforded by the most successful ships.