This document provides instructions for making one's own fly line from inexpensive, readily available materials. It summarizes: 1) Commercial fly lines can be expensive and inconsistent between manufacturers, but homemade lines only cost about $15 each to produce and can be tailored to an angler's rod and casting style. 2) The method was developed by John Betts and involves using braided Dacron for the inner and outer sheaths around a monofilament core, which are tapered by staggering the strands. 3) The process takes several hours but results in a line that casts and floats superiorly to commercial lines, is very durable, and allows anglers to reproduce customized lines that improve with use.