I've had this handy little app for years and I do refer to it at times. It's a free app and the advertising is minimal, just a banner across the bottom. I'm pretty particular about which apps get put on my devices and this is one of them. itunes: https://itunes.apple.com/us/app/knots-guide/id387892553?mt=8 google play: https://play.google.com/store/apps/details?id=com.max.KnotsGuide&hl=en_US I like it. I use it. That's my review.