If you don't have a http://ikkemunandar.blogspot.com /2015/02/how-to-wire-110-block.html" target="_blank">110 block you may have a 66 block in your home. Phone companies can charge a monthly inside wire maintenance fee if you want them to repair any issues that may occur with the phone wires inside your home. If you learn to maintain your own phone system you can save a decent amount of money. For me it's about $120 every year.
66 Block Components
The 66 block is normally mounted on an 89D Mounting Bracket to provide some clearance to run cables behind the 66 block.
Pins in the center of the block are were wires get connected. On a split 66 block there are 4 pins on each row. The first 2 pins on a row are electronically connected, as are the last 2 pins on a row but the 4 are independent of each other. If you connect a wire to pins 1 and 2 the signal from the wire on pin 1 will also flow to the wire on pin 2 but not to pins 3 and 4.
If you want the signal from pins 1 & 2 to flow to pins 3 & 4 you would install a metal bridge clip over pins 2 & 3.
A 50 Pair split 66 block will have 25 rows of pins which allow you to punch down 50 pairs of wires, 25 on each side. With old style 4 pair (green, red, black, yellow) telephone wire you can punch down 12 cables on each side. With newer style Cat5e wire (white-blue, blue, white-orange, orange, white-green, green, white-brown, brown) you can punch down 6 cables per side.
Fins on the sides of the 66 block are meant to keep wires separated from each other. Some of the fins are slightly rounded to help you identify every 10th wire. You can write on the fin with a permanent marker or apply labels to them for identification.
66 Block Vs 110 Block
Step 1: Installation
Step 2: Punch Down Incoming Phone Lines
Step 3: Punch Down Phone Jack Cables
I've highlighted the different cables with an orange box to make it easy to see in the illustration. Each cable will run to a different jack to allow one phone to be connected to it.