When pole manufacturers assemble a fishing pole, the common practice is to place the guide right on top of the blank and then hold it in place with thread. The thread is then cemented in place with epoxy. When the epoxy cures, along with the thread, it is what clamps the guide onto the blank.
The problem with this method is the foot of the guide does not always sit smoothly on the blank. The surface of the blank is not the ideal place to sit the guide on, but it is the cheapest way to do things. There usually are some air spaces left between the bottom of the guide foot and the surface of the blank.
When the assembler then puts thread over the top of the guide and epoxies the guide to the pole, there are air pockets and gaps where epoxy does not get to under the foot of the guide. These imperfections are the problem. In time, the guide can become loose and fail. It begins as a white spot under the surface of the epoxy along the length of the foot of the guide, and as it progresses the guide will begin to wiggle and then can fall off the pole.
To correct this situation, manufactures producing high quality fishing poles underwrap their guides to their blanks. What this means is, before the guides are placed on the poles, a layer of thread is applied onto the blank right below where the guide is going to sit. After the underwrapping is put on the blank, the guide is placed on top of the underwrapping thread. An overwrapping of thread is then wrapped around the foot of the guide and the blank. The feet of the guide is now sitting on the cushion of a layer of thread that conforms to the bottom surface of the foot of the guide. The overwrapping pulls the guide down onto the underwrapping thread and there are no air gaps to cause problems in the future. Then epoxy is applied to hold everything is place.
Using underwrapping method to hold the guides onto the blank, makes a more secure guide placement, holds more epoxy to better cement the guide in place and will prevent premature failure of your fishing pole.
Fish Big or Go Home