Drawing a Triquetra

It's pretty tricky to get this design to come out looking right without a lot of practice. Most of the problems you'll encounter revolve around keeping things even and symmetrical, so it may be best to either practice your circles a lot or use a computer to do the line work.

On a side note, you might have noticed that the triquetra is seen in the center of a trefoil, and if so you're not going to be very surprised to hear that the easiest means of handling a triquetra is almost the same as the method of drawing a trefoil using a triangle.

Here's a simple way to draw this difficult design:
Begin the drawing by stetching an equalateral triangle pointing up.
Work your way around the triangle, turning each side into a plus by adding the appropriate lines.
Place a mark towards the end of each line; the last eighth seems to work best.
Now that you have a useful set of guides, draw half-circles using the edges of the triangle and the lines inside the triangle.
Clean up your lines and you've created a well-made triquetra!