I assume you are meaning that you are turning it around a square corner?
If so, the best way to do that is to cut a 90 degree V out of the spine of it, with the point of the V centered on the corner.
That allows the spine part to meet perfectly inside the groove on the corner.
I agree with PacManFan about gluing the joint.
If it's going to be in a "high traffic area" like the edges of a CP or something, I wouldn't use hot glue though, I'd use epoxy.
Hot glue doesn't really stick to anything (especially plastics and vinyls), and will let it pull back out too easily.
If you get the 90 second setting epoxy, you can hold the pieces in place by hand.
The 5-minute kind gives you a little more working time, but you'll probably want to hold the pieces in place with a bar clamp until they set.