This little jig greatly speeds the laying out and marking of dovetail pins. Make the jig so the thin piece is exactly the same size as the pin you plan to use. Then, mark a half-pin on the left side, and divide the remaining space into equal parts according the the number of pins you want to use. Mark each full pin, from left to right, ending with another half-pin.
If you mark with a pencil, this is great. I use a marking knife, so I'd make the blade out of brass. Yes, it's a little more work to make the jig, but you don't run the risk of cutting into it with a marking knife and ruining it. What I really like about this, is the flexibility. You can make various sizes, or you can just use the smallest version you have and make larger pins by marking one edge, then sliding the jig to whatever size you want to mark the pin's other edge. Also, the original tip mentions equal spacing. If you want to make hand-cut dovetails that look as though they're machine-cut, then sure, equal spacing is the way to go. But if you're going to cut them by hand, why not take advantage of the freedom that affords and vary the spacing?