When David Boren served as a camp counselor in the Ore-Ida Council, his Scoutmaster challenged Boren's unit to learn 50 knots. Boren learned them all, went on to earn the Eagle Scout Award, and remains involved with Scouting as a Webelos Den leader and Cubmaster. Today, Boren is still fascinated by knots, which led him to create a great interactive app for mobile devices.

Knots 3D makes it easy to break each knot into steps, zoom in for detail, rotate to view them from different angles, and replay the process. Knots 3D teaches more than 50 knots, including the Alpine Butterfly, Backsplice, and Double Bowline. New knots are added frequently. $1.99 at the iOS App Store or Android Marketplace.