Unless you are a boy scout, you will want to have "Knots" on your PDA. The demo version of the application only includes one knot. The registered version has 6 useful knots for all occasions and only costs $10. All knots have been meticulously hand-drawn to show the step-by-step process to tie each knot. With the registered version you get... - Bowline: the best loop knot, bar none - Constrictor Knot: best for bundling loose materials - Fisherman's Knot: joining fishing lines (leader) - Sheet Bend: joining 2 ropes together (end to end) - Tautline Hitch: keeps a tight line (tent guy, clothesline) no sag. - Trucker's Hitch: best for cinching down loads