I have been asked about laying out the holes on the side boards. Assuming that the legs on the bench in the engraving are 10 feet apart on center, each set of holes is 2 feet wide. The vertical row of holes continues down the legs. The actual width of a 2x12 is 11 1/4 inches. If you make the vertical distance between the centers of the top and bottom rows of holes 7 inches, then the center of the holes on the diagonal will be 5 inches apart.
As long as the center of your legs is an even multiple of 2 feet apart, this will work. For an 8 foot bench with legs 6 feet on center there will be 3 sets of holes, for a 6 foot bench with legs 4 feet on center, there will be 2 sets of holes, etc.
7 inches makes the math works out evenly but, if you want other dimensions, just remember the Pythagorean Theorem. Add the square of the horizontal distance and the square of the vertical distance of each set of holes. Then take the square root of that number. That's the length of the diagonal. Divide by 5 to get the distance between holes. In my example, 7 squared plus 24 squared equals 625. The square root of 625 is 25. 25 divided by 5 is 5 inches between the centers of the holes measured along the diagonal. Of course, you can alter the number of holes as well.
If you'd like the vertical distance between the top and bottom row of holes to be 9", then the holes will be 5.126" apart along the diagonal. This is so close to 5 1/8" that I think we can call it good. Just measure from the top or bottom consistently.
Similarly, if you want the vertical distance to be 8", then holes placed at 5 1/16" intervals along the diagonal will be almost even. Just start from the same edge every time. In the end, 8" looked about right to me, so that's what I did.
As for the vertical holes, since there are three of them, the easiest thing to do is use dividers. That's probably how Nicholson would have laid out the holes on the diagonal too. Really no need to use a ruler at all if you want to skip the math.