Why? He isn't trying to trace anything. He's looking for an open circuit. He knows where the (only) cable starts and ends. He knows what pairs he used. (unless he cut them down wrong.) He hears dial tone at the raw wires. He just doesn't hear DT at the other side of the block, where the X-conns are cut down.
OK, I'll spell it out:
A test set (butt set) would be my first choice. Go the side of the 66M block where the incoming cable terminates. Is it a 66M25, 66M50, some other type? Do you hear dial tone? Put the clips exactly opposite the wires on the same block. Dial tone? No? You need bridging clips.
