What is a 66 block

66 Block is a Telecommunications connection terminal. It acts as a hub of distribution - usually for phone service or telephone extensions. Also referred-to as a "punch-down block" because of the impact tool used to fasten the wires onto the metal pins of the block.

[jamesodell]

So where would you punch down a fax line to feed off one of those pairs?

[michaelcostello]

Finally someone explained what it actually is. Thanks