The X part is the Crossing Point value for the knot and the Y part is the Saturation Index of the knot.
The concept of counting Crossing Points was first utilised by Geoffrey Budworth to assist forensic analysts to identify knots. The method was introduced in Knots & Crime, published by the Police Review Publishing Company in 1985.
In order to calculate the OI of a knot, simply count up the total number of times threads cross over other threads. Then to identify the knot, go to the OI page corresponding to that number of crossings and compare your unknown knot with other knots known to have that same number of crossings.
To see a few examples of how it's done take a look at these Counting Examples. Sometimes counting the Crossing points is enough to give a unique identification to a knot, but sometimes a particular OI group might have a number of knots sharing the same X value.. When this happens, the Saturation Index, the Y component should be calculated in order to refine your search. Go to these pages to learn how to calculate the Saturation of any particular knot.
| OI-1 | OI-2 | OI-3 | OI-4 | OI-5 |
| OI-6 | OI-7 | OI-8 | OI-9 | OI-10 |
| OI-11 | OI-12 | OI-13 | OI-14 | OI-115 |
| OI-16 | OI-17 | OI-18 | OI-19 | OI-20 |
| OI-21 | OI-22 | OI-23 | OI-24 | OI-25 |
| OI-26 | OI-27 | OI-28 | OI-29 | OI-30 |
....