Pattern Makers Dowels are precision location devices originally used for the accurate alignment of two halves of a mould used for casting molten metal. These days, railway modellers use them to ensure that the boards of their layouts line up so that trains don’t derail when crossing joints.
The two parts of a set of pattern maker’s dowels, male and female, with three countersunk screw holes each
The two parts of a set of pattern maker’s dowels joined, showing the pip that is used to mark the second board for drilling.
These two images are the best I could find on the internet, and far better than anything I could take myself. They’re from Pete Degnan’s Blog where he explains very well how to install them accurately. Trust me, it’s a right royal PITA if they’re even fractionally off. It’s as black and white as it working perfectly, or not at all.
How do I know this? Yep, you guessed it. I had to install mine twice. My advice? Follow Pete’s detailed instructions, not your instinct, or your father’s advice. It doesn’t matter how accurate you think you can measure something repeatedly, there’s no substitute for doing it once and cloning that.