We use these for trellising indeterminate tomatoes in our hoop house as well as supporting other crops in the garden.  All you need is to attach the tomahook up high, and clip or wind the plant around the string.  These hooks allow you to "lean and lower" your climbing plants.  The hooks are made of stainless steel which can support up to 75 pounds.  These hooks are pre-wound with 50 feet of  UV-resistant twine.