Do not blow this page off.
The 25-Pair to 66 Block holds the cabling key to the modern-day telephony copper backbone infrastructure.
If you grasp the color-code configuration - hey, that's it.
Read the page on cabling and you'll get what I mean. Also, check out the page on the 110 IDF. The 25-Pair 110 IDF follows the same color-code sequence.