The Skagit cast was originally conceived on the Skagit River in Washington State, and therefore the Skagit line (as it is now called) was designed for delivering and presenting heavy flies to those elusive deep lying fish (originally Steelhead's) which sometimes proved difficult to catch. These lines are basically short heavy heads which are generally made up of a section of floating line incorporating anything from T-8 to T-17 (very fast sinking line) at the tip to complete it's length and can be used to good effect when fishing for Salmon in larger deeper rivers both at home and abroad, as well as being particularly useful in extreme temperatures at both ends of the scale. The T scale refers to grains per foot e.g. T-8 means 8 grains per foot and T-17 means 17 grains per foot and everything in between and for anyone who wishes to know, there are almost fifteen and a half grains in a gram
(15.4323). The length, and therefore weight, of this (T number) line that you add to the end of your set up is entirely up to you, "within reason", and will often be dependant upon the fishing situation you find yourself faced with at that time.
The Skagit cast itself is not set in stone, and most people think that it is always a Circle "C" type cast, and although this particular technique lends itself to this application very well, then so does any cast we often categorise as a waterborne cast, sometimes referred to as a sustained anchor cast, such as the Double Spey for instance. Any cast that peels off the water into a delivery will work well.
Here are some important considerations when executing casts with these Skagit lines:
Try to avoid putting these heavy lines on fast (tippy) rods.
keep continuous tension on the line throughout the cast.
Do not rush the cast keep it smooth and progressive throughout.