When you’re bringing up a new circuit board, you need a place to attach test equipment ground clips.
Take a resistor lead from that pile you’ve been collecting (you do save snipped-off through-hole component leads, don’t you?), bend it into a sort of flattened horseshoe with the ends pointing out, and firmly solder the ends to a convenient point on the board’s ground plane, ideally near the power entry point.
It helps if you leave a nice spot for the thing; tiny boards with all surface-mount parts pose a problem.
Long dangly ground leads clipped to a distant part of the board are definitely not adequate for low-level or high-frequency analog probing, but when you’re just trying to figure out if the mumble thing is alive, this hack will do the trick.
For detailed stuff, get up close & personal with that odd little scope probe nosepiece you’ve been keeping in a bag for some reason.
The top board is, of course, the one you’ve seen earlier.
The Smell of Molten Projects in the Morning 