What pattern of cable design do you have. Many from books have been made into plastic stencils. However, it is difficult to advise without seeing the design or at least know the book it is in.
To the post about double blade knives - You are fortunate in have one of the Xacto double blade knives. They were discontinued back in the 90's. Olfa made one but they also have discontinued the manufacture. Stencils are certainly easier to make with the double blades. However, it is possibl to use the single blade and just do two cuts. It takes some care to get the cut even but it can be done. There is also an easy to cut plastic for stencils. It is called DBK and is a flexible blue plastic. Much easier to cut on this than the stiff plastic.