Hello Jerome,

You could create two Products: one called Rope Roll, this product you will use for purchasing the roll and track Quantity on Hand.

Then you need a product called Rope this will be for the individual lengths and you will need to add the Attrbute: Length and Attribute Values: 200', 400', 600', and 1200'.

Then I would create a Bill of Materials for each of the Variants. In the BOM set Component Product to Rope Roll and the QTY to 200, 400, 600, and 1200. If you have lots of color's it will be easier to import in the BOM's.

You could also create a Route on the Product to auto make a Manufacturing Order whenever the product sells or if you cut the rope in batches you can create the MO's manually.

This way you will always see your Total QOH for the Rope Roll.