Fretting jig for piccolo

Now what is going on here? I'm attempting to make a jig for cutting
fret slots in situ, after the neck has been attached. It's for making
sure the 12th fret comes in the right place. I do hope I'm not totally
wrong about this.

Jig will be in perspex and I'll most likely be using a hand saw for
cutting. The glue hardens in daylight, hence the position near the
window. And it smells really strong.