The answer is probably simple, but it’s just not computing in my brain and this is the first time I’ve done a project like this.

I’m making a small picket fence to go around the edge of a pond to form a barrier between the pond and a brick pathway, and we’ve decided we want it to mimic the pond shape at one end in order to close off a small gap our Labrador could feasibly access to fall into the pond (she’s 15 and a menace), so will have a smaller fence panel with maybe only 2 or 3 pickets. It’s hard to explain as this is a DIY pond - it’s in-ground with large vertical pavers reinforcing the sides, so it’s got an irregular shape. Pic is linked below, with the red arrows showing the fence line.

Once I find the inside angle of that fence corner/turn, how do I translate that to the angle I need to cut the ends of the railings for a mitre(?) joint? The angle will be greater than 90 degrees for clarity. I imagine it involves cutting at that angle, then rotating the smaller piece 180 degrees to form the joint?

Sorry for how painfully obvious my lack of knowledge is - this is a project for my grandparents’ garden trying to restore it to its former glory. I’ve spent months gradually renovating the pond when I had time (completely ripped out the old liner, cut back the tree trunk, fixed up the walls and increased depth etc before replacing liner and buying + setting yup new pump and filter - now finishing everyone needed before fish and plants go in - I’ve just replaced the pump to filter box tubing with black tubing too) and I’ve painted the railing and pickets too, but now I’m stuck.

Pic of pond linked here