I want to say it is a vertex but I could be caught in a lie there, I'll look and provide the exact answer. I have used it a number of times and it does a good job. I have a digital angle gauge that I bought at Home Cheepo, I think I spent 20 bucks for it and I can set it on my table, zero it out then set it on the angle plate/table (its magnetic) and adjust the plate until it reads the angle I am after and it is a pretty accurate method for cutting an angle in flat stock. I'll shoot a picture and post it tomorrow....