I am so excited about these Celting Knot Templates from TopAnchor! I'm going to tease you with this picture until later this week as it's such a beautiful day here that we're taking the kids up to the Blue Ridge Parkway for some hiking and fun.
The bigger size is one I used in my Craftsy class (25% off discount link!) and it will be available towards the end of the month. You can't see it in this picture, but there are 1/4 inch markings along the straight side and the half circle, so it is very versatile!