It -sounds- like you have all analog telephones.
But you mentioned CAT-5, which is for digital telephone
communications.

All the phone lines are for analog use. The DSL line is not involved
in this discussion because the phone company has added a DSL splitter
box to separate the DSL line from all the other phone lines that are
strictly for voices.

Most of the phone lines are old style 4 wires version
(red/green/black/yellow). However, there is one line that has 8 wires.
I believe it is the recently installed phone line that an electrician
installed it for me two years ago. The recently installed line is also
for voice only. Actually, I don't know if it is a cat-5 cable or not;
I was just guessing based on the fact that it has 8 wires.

Don't try to do those by twisting wires because there is an
impedance to the cable that depends on wiring positions
and spacing, and it must be maintained for best operation
of the phones. Simplest way would be just buy a single box
for each line, or a gang box, and plug the original lines into it,
the plug your extended wiring into the other side, and you're
done.

I think you are right in saying this. Last night, I tried to use a
junction box to connect two phone lines by twisting wires together, and
I didn't like it. This was time consuming. I had a feeling that the
physical connection was not that great. And I will have a long section
of untwisted wires inside the junction box. Of course, I disconnected
it. I think I will use a jack-and-plug pair to connect two sections of
phone lines together, and house all the jack-and-plug combos in a box
or something. I have already had a 110 punch down tool anyway, and I
find that making connection to a jack and plug is quite simple.
Thanks for the suggestion.

Jay Chan