The TCS®2.0 Solid Strip lines your rim first in a tubeless setup to prevent the tubeless tape from sagging into the spoke holes, thereby ensuring a smooth interface between your tyre and rim. It also prevents air from escaping through indents in the tubeless tape, making to tyre easier to mount.
Should you break a spoke, the Solid Strip will help to preserve the airtight nature of the system by preventing punctures, making the whole system more durable and simpler to set up.