Hey Ol'Bill, Like the old song goes "Old age won't kill you but it slows you down...". There are a few knot tying tools on the market but I have no experience with any of them. I would like to suggest to you another option. You could pre-tie some snelled evening favorites at home where light and temperature are better. Then just tie a perfection loop when fishing in the late afternoon and use loop connections for the rest of the day. Orvis carries a fly-box that has removable inserts that hold dropper rigs but it could be used to hold your dry & wet fly snells in addition to hopper/dropper rigs. I do not personally own this box yet but maybe our readership can tell us how they work. Tight Lines, RR