Take it from me: "You will most definitely come face-to-face with a telco configuration like the one below:
The Bridge Clips on the POP/Demarc 66 Block are essentially the demarcation point for the Local Exchange Carrier's Circuit.
If you experience problems on a Trunk or Line - you might be asked to lift the Bridge Clips to break the connection so that the circuit can be tested to the Demarc.
Note1: Telco jumpers are usually color coded: Yellow/Blue - Blue/Yellow!
Note2: Special copper circuits (T1's, Frame Relay, Switched 56) are not Bridged.
Most special circuits will jumpered on a 2-pair Cross-Connect* to a Smart Jack/Westel.
* Red/Blue - Blue/Red and Orange/Red - Red/Orange