Point to you. Prusik Knot is correct.

http://storrick.cnchost.com/Vertical...notPrusik.html

http://lasr.cs.ucla.edu/geoff/prusik_knot.html

A friend of mine used two of these today. They can be also be
used with the second one with two ends instead of a loop--one
to each foot ending in a slip knot.

It's also noteworthy that the ascender line should be smaller
diameter line than the fixed line you are ascending.

For sailors, using a safety line--second halyard, makes the descent
much easier and faster.

It is a very easy knot to tie, and it's always a good idea to
have some smaller diameter, high strength line laying around
for such purposes. I used to carry a coil of small line in
my lifejacket, and used it often when sailing on other peoples
boats--several times they tried to keep it!

In any event, this is another example of the similarity between
climbing and sailing--both sports rely heavily on knots and
line.

wrote

Prusiks. I have tried the so-called Bachmann knot as well but they did
not work well on muddy rope although easier to "break". I tried one
other but cannot remember its name. I can tie prusiks with my eyes
closed or in total darkness (being a caver) and have climbed many
thousands of feet on them including out of the worlds deepest pit.
BTW, it better be three prusiks, not two. You need one for your chest
and one for each foot although in a pinch you MIGHT get by with a
single one for both feet.