General information on the rope and knots
used in mushing.
There are two types of hollow,
diamond braided, rope used to make the lines used in mushing. The first and most
popular is polyethylene and the other is polypropylene. Polyethylene is more
flexible at lower temperatures but polypropylene is said to be more abrasion
resistant. Both are available in either 8 or 16 braid (that's the number of bundled
strands) and come in a variety of colors. How can you tell if it polyethylene or
polypropylene? Easy, put a sharp crease in the rope. Polyethylene will tend to
hold the crease while polypropylene won't. That makes polypropylene harder to make
tight knots. Why use diamond braided poly instead of something else? It's
property to give a little under load, inherent stiffness and the ease of making
loops make this the preferred material. 
When making loops, it is a good practice to slightly melt the freshly cut end of the rope as it will make it easier to construct the knots and it won't fray as much. To make the loops, you will need a 'fid' to fit the size rope you are working with. This a short piece of hollow plastic or aluminum with a point on one end, shaped much like the forward barrel of a ball point pen. It is slipped over the end of the rope and allows you to thread the rope through itself to make the knots.
The following loops are used in
making parts of the gangline and other items you will find useful. When making the
loops, allow enough material to make the loop, plus the knot itself, plus another 4 to 6
inches to hide the extra tail inside the main line. The trick is to always make the
knot a locking type knot. That is, the tail is usually threaded through itself to
keep from pulling the knot open.
Knot 1: First insert the
tail of the rope inside the middle of the main line and come back out about 5 or 6 braids
down. Then insert the tail straight through the main line and tail inside of it,
about 1 or 2 braid above the last exit point. This locks the knot. Finally,
insert the remainder of the tail inside the main line, a braid or two below the first exit
point and pull tight. 
Knot 2: This is a simpler
version of Knot 1 but not quite as strong because the lock only goes through one side of
the main line. First insert the tail of the rope through main line. Second, go
back into the main line just above the first exit point and down through the tail and the
middle of the main line. Finally, pull the knot tight. 
Knot
3: This is another variation of knot 2
except it is a stronger knot because the lock goes through both the main line and the tail
before the tail is hidden. First insert the tail of the rope through main
line. Second, go back through both the main line and the tail above the exit point.
Finally, insert the remaining tail back into the main line below the first exit point and
pull the knot tight. This knot is perferred over knot 2. 
Knot 4: This knot is great for the end of a
leash. The problem is, you can only use it in one end of the line. First weave
the tail back and forth through the main line three times. Second pull the loops
snug and then thread the main line through the tail just below the last exit
point. This locks the knot. Finally thread the tail inside the middle of the
main line to hide it.