At a recent class on fly line technology, I was asked about over-lining and under-lining fly rods. I thought I’d share some of my thoughts on the subject that may help you with your casting. The subject begins in the mid-60’s when very flexilble slow-action cane and fiberglass rods required a very careful touch to avoid abrupt power application and resulting tailing loops. Anglers were quick to under-line these rods to create the illusion that the rod was faster or stiffer than it actually was. In the 80’s, the advent of high modulus graphite created a considerably less flexible, faster action rod. As a result, anglers began to overline these rods in an effort to make them load more easily. Today, there are hundreds of rods of virtually every conceivable action available to fly anglers. Yet anglers continue to over and under-line their rods.