Dazed and Confused

Ever wonder why the letter system on fly line was changed to a number system and why the grains never seem to match up to the rods exactly? You do get the sense that the folks who make the lines are only vaguely acquainted with those who make the rods. Yea man! It cast like a 5 wt., but a 4wt. will do it some real justice! Confused try buying a sinking line. I would like the bleeping fly to get down to the bottom or just off the bottom of (pick your favorite trout pond anywhere) lake. The fish seem to hold at 18 feet so what do I buy? Bring a comfortable chair as the sales guy/gal launch into techno babble about density, sink rates and ...... you get my drift. Dazed and confused, screw it , I'll fish the hatch!