X-Cycles are similar to Singles Chains in their use of links between similarly numbered candidates within a unit (row, column or box).
Links are classed as

**Strong Links** (dark green) if the candidates they connect are the only two of that value in the unit, or

**Weak
Links** (light green) if there are additional candidates of the same value within the unit. A group of such links becomes an X-Cycle if they
join together to form a complete loop. An X-Cycle is subject to Rule 3 if it meets the following criteria:-

- It contains an odd number of links.
- There is exactly one example of consecutive weak links.
- All strong links occur in groups having an odd number of members.

This puzzle contains such a loop for candidates of value 2. If you examine the loop you will soon convince yourself of the truth of Rule 3
which states that the candidate at the junction between two weak links must constitute a non-solution and may be removed.