At college, when doing clinker planking, we drilled the holes for the roved nails “by eye.” Mostly, we were fairly close or on target but, unless you have a lot of experience, it is difficult to be accurate.

Getting the copper roves running up the hull, in straight lines, at right ankles to the keel, and equally set in from the plank edges is the goal.

To try and achieve that goal, I have made a drill guide using two metal guides, and a couple of short metal rods. One of the arms is free to move up and down the rods.

Siting the nail on the target point on the inside of the boat, then angling the jig, so that the drill bit is on the line marking the midpoint of the plank below, I can hit the nail spot on 90% of the time, and if I’m “out,” it’s within 1-1.5 mm.

Although I can do this single handed, it is even easier with a helper ensuring that the top nail doesn’t drift from the target point above.

The overlap between planks in a clinker built boat is called the land. The copper nail should pass from the mid point of the land on the outside of the lower edge of the plank to the midpoint of the land on the inside of the lower plank – as shown below.

So here’s my simple jig:

Yes, there is a little “play,” but it give me much better results than just judging it by eye.

And here’s the result: