I have a gotten a couple emails regarding this practice ring so I thought I'd do a blog entry on it. They are easy to make, obviously, and there are a couple of tricks I use to make them more convenient than just a ring on a string.
The first thing you need is a three ply string with loops on both ends. The reason I make mine three ply is to guard against losing the ring due to nailing the string with a dart, which has happened to me twice. This way, if you nail a string and break it you have a couple more to keep your ring from clattering to the floor. To make the 3-ply string: start with an excessively long length of normal sewing thread, fold it into thirds, and then, before tying your overhand knot in the end, fold over all three of the threads once more. With the end of your 3-ply string completely doubled over tie your overhand knot, this ensures that your triple redundancy exists in the loops as well as the length between the ring and the needle.
The ring itself is a simple keychain ring. The diameter of the bull is 1.25 inches. Unfortunately I could not find a keychain ring the exact same diameter, but I did find one slightly smaller at 1.125 inches. Good enough for me.
The part that sticks in the board: I tried several different ideas, all of which had failings. I started with a simple pin (such as one finds in brand new button down shirts), but this had the problem of the loop in the thread slipping off too frequently when you nick the ring with your dart and it goes flailing about. So I then tried using a normal thumb tack, and tightening the string around it so it would not slip off the end of it but this had problems too. The thumb tack is too big and I would frequently hit it. Either destroying it ot knocking it out of the board. Then I decided to try the approach I now use. Use some wire cutters to snip off the needle and spring of a cloths pin. Then thread the loop in the string into the spring of the clothspin and you have a near perfect system.
The string will not slip off either the ring or the pin holding it to the board and the string is triple redundant. Furthermore, it is easily move to any part of the board. if you feel you need practice with the other triples (as I definitely do!).
As always, click the image for a larger picture.