If the line in question is a "digital" line, the standard butt set won't work. What I do in that case is I take a RJ-45 jack and wire pins 4 and 5 to a jumper cable. I then punch down the jumper cable to the points along the path and use the same model phone as the line is configured for to test the line. It's a bit more cumbersome, but it gets the job done.
This concludes my series on basic telephony and I hope it has been useful to other router jockeys out there that have been put in the situation of learning telephony too.