This very popular and highly rated app is free again. Get it if you have missed it previously.
iOS link: https://apps.apple.com/au/app/knots-3d/id453571750 Expired
From the website:
Used by arborists, fishermen, firefighters, climbers, military and boy and girl scouts the world over, Knots 3D will quickly teach you how to tie even the most difficult knot!
Accolades
• Google Play Editors' Choice designation
• Winner of Google Play Best of 2017, Hidden Gem category.
• Included in Scouting Magazine's "Best Scouting Apps of 2016"
With more than 150 knots, Knots 3D will be your go-to reference! Grab some rope and have fun!
Permissions:
NO INTERNET OR OTHER PERMISSIONS REQUIRED! Completely self contained.
Product Features and Functions:
• 152 unique knots with new ones added frequently.
• Browse by category or search by name, common synonym or ABOK #.
• Landscape and portrait modes and full screen (zoom in to see greater detail).
• Watch knots tie themselves and pause or adjust the speed of the animation at any time .
• Rotate knots in 360 degree, 3D views to study them from any angle.
• Interact with the knot on screen by "scrubbing" your finger over the knot to advance or rewind the animation.
• Dark mode / Light Mode
• No advertisements. No in-app purchases. No subscriptions. Ever!
7 Day Refund Policy
Try Knots 3D risk free for a week. If you would like to request a refund, send the order number found in the receipt Google emails you at the time of purchase to our support email address.
Languages:
English, Arabic, Chinese, Czech, Danish, Dutch, Finnish, French, German, Greek, Hebrew, Italian, Japanese, Korean, Norwegian, Polish, Portuguese, Russian, Spanish, Swedish and Turkish!
The entire list of knots can be found here:
Enjoy!
Free on iOS as well - heading now updated by OP already so happy for Mod to delete comment